$\text{As on day 20 of the production calendar, the corresponding due date and work remaining are given in the table.}$

$\text{<br>}$

Job	Due Date	Work remaining
$M$	$26$	$5$
$N$	$24$	$10$
$O$	$28$	$10$
$P$	$31$	$5$

$\text{Which job(s) has/have critical ratio less than unity?}$

The correct option is Job N & O.

To determine which jobs have a critical ratio less than unity (1), we first need to understand the definition and formula for the Critical Ratio (CR).
The Critical Ratio is a scheduling rule used to determine the priority of jobs. It is calculated using the following formula:

$\mathrm{Critical\; Ratio\; (CR)}=\frac{\mathrm{Due\; Date}-\mathrm{Current\; Date}}{\mathrm{Work\; Remaining}}$

According to the problem description, the current date (as on the production calendar) is day 20.
Therefore, the formula for each job simplifies to:

$\mathrm{CR}=\frac{\mathrm{Due\; Date}-20}{\mathrm{Work\; Remaining}}$

Now, we calculate the critical ratio for each job listed in the table:

1. For Job M:
Due Date = 26, Work Remaining = 5

${\mathrm{CR}}_M=\frac{26-20}{5}=\frac{6}{5}=1.2$

Since 1.2 is greater than 1, Job M has a critical ratio greater than unity.

2. For Job N:
Due Date = 24, Work Remaining = 10

${\mathrm{CR}}_N=\frac{24-20}{10}=\frac{4}{10}=0.4$

Since 0.4 is less than 1, Job N has a critical ratio less than unity.

3. For Job O:
Due Date = 28, Work Remaining = 10

${\mathrm{CR}}_O=\frac{28-20}{10}=\frac{8}{10}=0.8$

Since 0.8 is less than 1, Job O has a critical ratio less than unity.

4. For Job P:
Due Date = 31, Work Remaining = 5

${\mathrm{CR}}_P=\frac{31-20}{5}=\frac{11}{5}=2.2$

Since 2.2 is greater than 1, Job P has a critical ratio greater than unity.

Comparing the calculated critical ratios, we find that Job N (CR = 0.4) and Job O (CR = 0.8) are the jobs that have a critical ratio less than unity.