If f(x) = 7x^5 - 3, then f ^-1(x) =

a. [(x + 7)/5]1/3
b. [(x + 3)/5]1/7
c. [(x + 5)/7]1/3
d. [(x + 7)/3]1/5
e. [(x + 3)/7]1/5
f. [(x + 5)/3]1/7
g. none of these