Landry bought 11 binders and notepads from the market and spent $45. Binders cost $6 each and notepads cost $2.50 each. Which two equations can be used to find the number of binders, b, and notepads, n, she purchased?
(A) b + n = 11 (B) 6b + 2.5n = 11 (C) b + n = 45 (D) 6b + 2.5n = 45