Lauren is considering buying one of the four popular e-readers where the e-reader’s premium services is a monthly charge. The function A1 (t) = 5t + 350, A2 (t) = 10t + 250, A3(t) = 499, and A4 (t) = 15t + 179 model the total amount of money A, in dollars that Lauren spends after buying the e-reader and subscribing to t months of e-reader’s premium services. Which e-reader has the greatest monthly subscription cost?

a. E-reader 1 with cost A1(t)
b. E-reader 2 with cost A2(t)
c. E-reader 3 with cost A3(t)
d. E-reader 4 with cost A4(t)