Here's what I did:
W0 = (4.58 eV) (1.6e-19) = 7.33e-19 J
Kmax = hf - W0
f = (Kmax / h) + W0
f = (6.48e-19 / 6.626e-34) + 7.33e-19 = 9.78e14 Hz
But that's not the right answer. The right answer is supposedly 2.08e15.
Your setup is totally fine. Your equations are correct. Your problem lies in your algebra.
This solution provides a brief outline on the mistake in the problem, involving frequency calculations.