GAUSS8 2000 Problem 11

Pat planned to place patio stones in a rectangular garden that has dimensions 15\:m by 2\:m. If each patio stone measures 0.5\:m by 0.5\:m, how many stones are needed to cover the garden?

Answer Choices
A. 240
B. 180
C. 120
D. 60
E. 30