Explanation:

- Suhani's income is Rs. 90,000 with a 30% tax rate. So, she pays Rs. 27,000 in taxes.

- Ritika's income is Rs. y with a 40% tax rate. She pays 0.4y in taxes.

- Combined income of Suhani and Ritika equals Rs. 90,000 + Rs. y.

- Total tax paid together should be 37% of their combined income. This equals 0.37 × (90,000 + y).

So, we set up the equation for combined taxes:

$$

27,000 + 0.4y = 0.37 \times (90,000 + y)

$$

Solve for y:

$$

27,000 + 0.4y = 33,300 + 0.37y

$$

Simplifying gives:

$$

0.03y = 6,300

$$

Solving for y:

$$

y = 210,000

$$

- The correct option is Option 4: Rs. 210,000.

.