A valid password on a Web site contains 3 letters (A-Z, 26 total), followed by 3 digits (0-9). Letters and numbers can be repeated. The number of possible passwords equals _____.

A. 26*25*24+10*9*8

B. 26^3+10^3

C. 26^3*10^3

D.26*25*24*10*9*8