In a city, car plates are composed of 7 digits. Among them, the former digits should all be letters from the 26 alphabets, while the latter digits should all be numbers from 0 to 9.

x: The number of possible different car plates when choosing four letters(A-Z) and three numbers(0-9),numbers and letters can be used more than once.

y: The number of possible different car plates when choosing four letters(A-Z) and three numbers(0-9),numbers and letters can not be used more than once.

z: The number of possible different car plates when choosing three letters(A-Z) and four numbers(0-9),numbers and letters can be used more than once.

Quantity A	Quantity B
x-y	z

A. Quantity A is greater
B. Quantity B is greater
C. The two quantities are equal
D. The relationship cannot be determined from the information given