A person bought two bicycles for Rs.1600 and sold the first at 10% profit and the second at 20% profit. If he sold the first at 20% profit and the second at 10% profit, he would get Rs.5 more. The difference in the cost price of the two bicycles was :

• A. Rs. 25
• B. Rs.75
• C. Rs.50
• D. Rs.40