The Quantity Q of Grapefruits Demanded at Price P Is

The quantity q of grapefruits demanded at price p is given by q = 30 - 3p and the supply schedule by q = 6p. The government imposes a quantity tax at some rate t, which it collects from buyers. What is the smallest tax rate that will result in no grapefruits being bought or sold?

A) 10%
B) 3.33%
C) 3.67%
D) 11.50%
E) 13%