Healthy Bites is a fast food joint serving three items: burgers, fries and ice cream. It has two employees Anish and Bani who prepare the items ordered by the clients. Preparation time is 10 minutes for a burger and 2 minutes for an order of ice cream. An employee can prepare only one of these items at a time. The fries are prepared in an automatic fryer which can prepare up to 3 portions of fries at a time, and takes 5 minutes irrespective of the number of portions. The fryer does not need an employee to constantly attend to it, and we can ignore the time taken by an employee to start and stop the fryer; thus, an employee can be engaged in preparing other items while the frying is on. However fries cannot be prepared in anticipation of future orders. Healthy Bites wishes to serve the orders as early as possible. The individual items in any order are served as and when ready; however, the order is considered to be completely served only when all the items of that order are served.

The table below gives the orders of three clients and the times at which they placed their orders:

Client No.	Time	Order
1	10:00	1 burger, 3 portions of fries, 1 order of ice cream
2	10:05	2 portions of fries, 1 order of ice cream
3	10:07	1 burger, 1 portion of fries

Assume that only one client's order can be processed at any given point of time. So, Anish or Bani cannot start preparing a new order while a previous order is being prepared.

Suppose the employees are allowed to process multiple orders at a time, but the preference would be to finish orders of clients who placed their orders earlier. Also assume that the fourth client came in only at 10:35. Between 10:00 and 10:30, for how many minutes is exactly one of the employees idle?

The correct option is B.

Let's track the status of both employees (Anish and Bani) minute-by-minute from 10:00 to 10:30 to find when exactly one of them is idle.

1. From 10:00 to 10:02:
- Anish is preparing Client 1's burger (Busy).
- Bani is preparing Client 1's ice cream (Busy).
- Idle employees: 0.

2. From 10:02 to 10:05:
- Anish is preparing Client 1's burger (Busy).
- Bani has completed the ice cream and is idle (Idle).
- Exactly one employee is idle: Bani. (Duration = 3 minutes: 10:02 to 10:05).

3. From 10:05 to 10:07:
- Anish is preparing Client 1's burger (Busy).
- Bani starts preparing Client 2's ice cream at 10:05 (Busy).
- Idle employees: 0.

4. From 10:07 to 10:17:
- Anish is preparing Client 1's burger until 10:10 (Busy). At 10:10, Anish finishes and becomes idle.
- Bani finishes Client 2's ice cream at 10:07. Since Client 3's order (1 burger, 1 portion of fries) was placed at 10:07, and Bani is free, she immediately starts preparing Client 3's burger at 10:07. This takes 10 minutes, so she is busy from 10:07 to 10:17 (Busy).
- Let's check the sub-intervals here:
- From 10:07 to 10:10: Anish is busy, Bani is busy. (0 idle).
- From 10:10 to 10:17: Anish is idle, Bani is busy. (Exactly 1 employee is idle: Anish. Duration = 7 minutes: 10:10 to 10:17).

Wait, let's check what happens after 10:17:
- At 10:17, Bani finishes Client 3's burger. Since there are no more orders until 10:35, both Anish and Bani are idle from 10:17 to 10:30. (2 idle employees).
- Sum of durations where exactly one employee is idle:
- From 10:02 to 10:05 (3 minutes)
- From 10:10 to 10:17 (7 minutes)
- Total = 3 + 7 = 10 minutes? Or is it 7 minutes? Let's check the options: A) 7, B) 10, C) 15, D) 23.
Wait, if the answer is 7 (Option A) or 10 (Option B), let's examine why it could be 7. What if Bani starts the ice cream for Client 2 at 10:10? If she starts at 10:10:
- From 10:02 to 10:10, Bani is idle. Anish is busy (10:00 to 10:10). Exactly one employee is idle: Bani (8 minutes).
- At 10:10, Bani starts ice cream (ready at 10:12) and Anish starts burger (ready at 10:20). Then exactly one employee is idle from 10:12 to 10:20 (8 minutes). This would give a different sum.
But if the standard timeline is:
- 10:02 to 10:05 (3 mins, Bani idle)
- 10:10 to 10:17 (7 mins, Anish idle)
Total = 10 minutes. If the official answer is 7 minutes, it corresponds to the duration of the second idle period (10:10 to 10:17). Let's note that 7 is one of the options (Option A), and 10 is also an option (Option B). Let's state the calculations clearly for both interpretations.