A bookstore sells paperback fiction books in excellent condition for $2.50 and in fair condition for $0.50. Write an expression for the cost of buying 'x' excellent-condition paperbacks and 'f' fair-condition paperbacks A) 2.50x + 0.50f B) 3.00 (x + f) C) 2.50f + 0.50c D) 3.00 + x+f