**Answer**: (A) Rs 150

**Explanation**: Let Cost Price = Rs 100, Selling Price = Rs 120

If Cost Price = Rs 40

Profit = 50%, hence Selling Price = (40 * 150)/100 = Rs 60

Difference of Selling Price = (120 – 60) = Rs 60

When difference is Rs 60, Cost Price = 100

When difference is 90, Cost Price = Rs 150