I'm revising for an upcoming Haskell exam and I don't understand one of the questions on a past paper. Google turns up nothing useful

fst(x, y) = x
square i = i * i

i) Source reduce, using Haskells lazy evaluation, the expression:

fst(square(3+4), square 8)

ii) Source reduce, using strict evaluation, the same expression

iii) State one advantage of lazy evaluation and one advantage of strict evaluation