Correct Answer - Option 4 : Rs. 31,800
Let, Sapna's monthly income is Rs. 100
Given information,
Sapna invests her monthly income in mutual Fund = 18%
And she invests in mutual funds = Rs. 5,724
Then,
18% = 5,724
1% = 5,724 / 18
1% = 318
Now, 100% = 318 x 100 = 31,800
So, Sapna's monthly income will be 31,800.
Hence, "31800" is the correct answer.