if z(t) = 60 * 1.03^t, find t when z(t) = 144

60 * 1.03^t= 144

1.03^t = 2.4
take log of both sides
log 1.03^t = log 2.4
t log 1.03 = log 2.4
t = log 2.4/log 1.03 = appr 29.6