Find the number of items sold per month 33 months after the item first becomes available

The sales of a new product (in items per month) can be approximated by S(x) = 325 + 400 log(3t + 1), where t represents the number of months after the item first becomes available. Find the number of items sold per month 33 months after the item first becomes available.
Thanks in advance.

This is nothing more than a substitution question:
Substitute t = 33 and use your calculator to evaluate.

S(33) = 325 + 400*log(99 + 1)
You don't even need the calculator!!

S(33) = 325 + 400*log(100)
.......... = 325 + 400*2
.......... = 1125