a 50-mg sample of cobalt-60 decays to 40mg after 1.6min. determine the half-life of the cobalt-60.

this is as far as i got before getting stuck

M = C $\displaystyle (\frac{1}{2})^\frac{t}{h}$

40 = 50 $\displaystyle (0.5)^\frac{1.6}{h}$

0.8 = $\displaystyle (0.5)^\frac{1.6}{h}$

$\displaystyle \frac{1.6}{h}$ = $\displaystyle \frac{log0.8}{log0.5}$

then right here i get stuck and can't get the correct answer. can somone tell me what i'm doing wrong?

i'm getting the answer 0.52 mins, when its susposed to be 5 mins