Grant is a member of a book club. he pays a $10 yearly membership fee and can purchase books through the club for $2.75 each. his total annual cost is a function of the number of books, b, that he purchases in a year: c(b) = 2.75b + 10 which statements are true about the variables in the yearly cost function? check all that apply. the number of books purchased is the independent variable. the input is the yearly cost. the total yearly cost depends on the number of books purchased. the number of books purchased is determined by the yearly cost. the output is the yearly cost.