The model is  


y = 900*e^(k*t).


You are given that y = 1305 at t =10.  Write it as an equation:


1305 = 900*e^(k*10).


It is equivalent to  (after dividing both sides by 900):


 = ,   or    = 1.45.


Take the natural logarithm of both sides:


k*10 = ln(1.45)  ====>  10k = 0.37156  ====>  k =  = 0.037156.


Thus the model is  y = .


Time to double:


1800 =   ====>  


2 = .


Take the natural logarithm of both sides:


ln(2) = 0.037156*t  ====>  t =  =  = 18.65 years.


Answer. Annual rate is   = 1.038.

        Equivalent annual percentage rate is 3.8% (considered as annually compounded)

        Time to double is 18.65 years.