There are 81 cars in the CMC parking lot, which are all Acuras, Beetles, or Camrys. There are half as many Acuras as Beetles. The number of Camrys is 80\% of the number of Acuras and Beetles together. How many of the 81 cars are Beetles?
Answer Choices
A. 36
B. 30
C. 45
D. 51
E. 66