In each of the following, f: Z+ → R. Solve for f(n) relative to the given set S, and determine the appropriate "big-Oh" form for f on S.
(a) f(l) = 0
F(n) = 2f(n/5) + 3, n = 5, 25, 125, . . .
S = {5ʹ| i ∈ N}
(b) f(1) = 1
f(n) = f(n/2) + 2, n = 2, 4, 8, . . .
5 = {2ʹ|i ∈ N}