There are several vehicles in a parking lot. Some of them are motorcycles (with 2 wheels), and some are cars (with 4 wheels). There are 12 vehicles in the lot, and there are 40 wheels. How many vehicles of each type are in the lot?
A. 5 motorcycles and 7 cars
B. 6 motorcycles and 7 cars
C. 8 motorcycles and 4 cars
D. 4 motorcycles and 8 cars