In 2014, the cost to mail a letter was 49 cents for up to one ounce. every additional ounce cost 21 cents. which recursive function could be used to determine the cost of a 3-ounce letter, in cents?
a. a₁ = 49; aₓ = aₓ₋₁ + 21
b. a₁ = 0; aₓ = 49aₓ₋₁+21
c. a₁ = 0; aₓ = aₓ₋₁ + 49
d. a₁ = 0; aₓ = 21aₓ₋₁ + 49
(in the answer selection above, i used x's instead of n's because i couldn't find the subscript for n. i don't know if that makes a difference or not.)
(this question is worth 25 points