For each of the following, find all values of p R for which f is improperly

Question:

For each of the following, find all values of p ∈ R for which f is improperly integrable on I.
a) f(x) = 1/xp I = (l, ∞)
b) f(x) = l/xp, I = (0, 1)
c) f(x) = 1/(x logp x), I = (e, ∞)
d) f(x) = 1/(1/ xp), I = (0, ∞)
e) f(x) = loga x/xp, where a > 0 is fixed, and I = (1, ∞)