A shopkeeper purchased 90 pens and the cost price of each pen is Rs. 10 and he sold it in two parts, the first part at 20% profit and sold the second part at 10% profit. If he sold all 90 pens at a certain price and got a 15% profit. If the profit earns in the second condition is more than the first condition and the difference in profits from both the conditions is Rs. 40. Find how many pens were sold at 20% profit.

• A. 10
• B. 15
• C. 5
• D. 20
• E. 8