Statistics: Exponential Growth calculations help !!

Hi everyone

I have encountered a problem while doing my statisticcs workbook. Please help me and provide an explaination on how you get there.

I have a population of bugs that reproduces exponentially. It has a doubling time of 2 hours. 15 milligramss is the starting mass (initial)

The problem that i am having is getting the (K) for the formula of exponential growth.
P=P0xe^kt

K is the rate of growth..I dont know what it is..Please help! I only know the doubling time is 2 hours. and the mass will 30mg at that time.

Please help me find K (rate of growth) for this formula

Thank you very much!

P=Poxe^kt
Population doubles in 2hrs. And so Po =1 becomes P = 2 in time t = 2.
Therefore, 2=1xe^k2
2 = e^2k
ln2 = 2k
k = (ln2)/2 = 0.6931/2=0.3466