[Grade 12 Math] Logarithms

The number of people investing in a mutual fund at a bank is modelled by the function p(t)=245(1.15)^t where t is the time in months, and p is the number of people.

a)How many people have invested in the mutual fun after 10 months? b)How many months does it take for 2000 people to invest in the mutual fund?

I am stuck on b). I cannot understand where the logarithms come in. Can someone give me a tiny push in the right direction?