A baker buys three cartons each with 6 eggs, two cartons each with 12 eggs, and twenty cartons each with 18 eggs. Which expression represents the problem?
a. (3 + 6) x (2 + 12) x (20 + 18)
b. (3 x 6) + (2 x 12) + (20 x 18)
c. (25 + 6) x (25 + 12) x (25 + 18)
d. (25 x 6) + (25 x 12) + (25 x 18)