You Can Now Sell 200 Cups of Lemonade at 60

Multiple Choice

You can now sell 200 cups of lemonade at 60 cents per cup, but demand is dropping at a rate of 10 cups per week each week. Assuming that raising the price doesn't affect the demand, how fast do you have to raise your price if you want to keep the revenue constant?

A) 3 cents per week
B) 6 cents per week
C) 5 cents per week
D) 2 cents per week
E) 7 cents per week