The cost in dollars to produce x cups of lemonade is represented by the function C(x)=10+0.20x. The revenue in dollars earned by selling x cups of lemonade is represented by the function R(x)=0.50x. What is the minimum number of whole cups of lemonade that must be sold for the revenue to exceed the cost?

33 cups
33.33 cups
33.67 cups
34 cups