Hi

I need help on the following question:

If prices are increasing at the rate of 7.8% per year write down an equation for prices as a function of time. How long does it take for prices to double? How long does it take for prices to treble?

I have found the equation:

To find t i transpose the equation to get:

now i don't know how to find how long does it take for prices to double or treble, because what will the values be for P and Po?

P.S