A invested some money in 4% stock at 96. Now, B wants to invest in an equally good 5% stock. B must purchase a stock worth of:

A. 120
B. 124
C. 76.80
D. 80
Answer: A

Explanation: 

For an income of Rs. 4, investment = Rs. 96
For an income of Rs. 5, investment = Rs. (96/4 x 5)
                                                     = 120.