Read the following information carefully and answer the questions given below. The information about three sellers who sold two types of rice, i.e., brown and white.

The quantity of white rice sold by all three seller is 230 kg. The quantity of brown rice sold by B is 20% more than the quantity of white rice sold by A. The quantity of white rice sold by B is 20 kg more than that of brown rice. The ratio of brown rice sold by A to B is 2:3. The average quantity of brown rice sold by all three sellers is 60 kg, and the total rice (white and brown) sold by C is 75 kg.

If the price of each kg of white rice sold by A is Rs 20 and the total revenue earned by A to sell all the quantity of rice (brown + white) is Rs 2580, then find the price of each kg of brown rice sold.

The correct answer is 18.

Let us solve the problem step-by-step by defining variables for the quantity of white and brown rice sold by each seller (A, B, and C):
Let $W_A$, $W_B$, and $W_C$ be the quantities of white rice (in kg) sold by A, B, and C, respectively.
Let $B_A$, $B_B$, and $B_C$ be the quantities of brown rice (in kg) sold by A, B, and C, respectively.

Step 1: Set up the equations based on the given information.

1. The total quantity of white rice sold by all three sellers is 230 kg:
$W_A+W_B+W_C=230$

2. The quantity of brown rice sold by B is 20% more than the quantity of white rice sold by A:
$B_B=1.2W_A$

3. The quantity of white rice sold by B is 20 kg more than that of brown rice sold by B:
$W_B=B_B+20=1.2W_A+20$

4. The ratio of brown rice sold by A to B is 2:3:
$B_A=\frac{2}{3}{B}_B=\frac{2}{3}\left(1.2W_A\right)=0.8W_A$

5. The average quantity of brown rice sold by all three sellers is 60 kg, which means the total brown rice sold is 180 kg:
$B_A+B_B+B_C=180$

6. The total rice (white and brown) sold by C is 75 kg:
$W_C+B_C=75$

Step 2: Express all variables in terms of $W_A$ to find its value.

From the total white rice equation:
$W_A+(1.2W_A+20)+W_C=230$
$2.2W_A+W_C=210$
$W_C=210-2.2W_A$

From the total brown rice equation:
$0.8W_A+1.2W_A+B_C=180$
$2W_A+B_C=180$
$B_C=180-2W_A$

Substitute $W_C$ and $B_C$ into the equation for seller C's total rice:
$(210-2.2W_A)+(180-2W_A)=75$
$390-4.2W_A=75$
$4.2W_A=315$
$W_A=\frac{315}{4.2}=75kg$

Step 3: Calculate the quantity of brown rice sold by A.

Using the relation for A's brown rice:
$B_A=0.8\times 75=60kg$

Step 4: Calculate the price per kg of brown rice sold by A.

Seller A sold 75 kg of white rice and 60 kg of brown rice.
Price of white rice sold by A = Rs 20 per kg.
Revenue from white rice = $75\times 20=Rs1500$.
Total revenue earned by A = Rs 2580.
Revenue from brown rice = $2580-1500=Rs1080$.
Price of brown rice per kg = $\frac{1080}{60}=Rs18$.