Suppose i had this equation , which i do , well i have one similar.

I keep getting stuck on finding the inverse becuase of so many things in it , i am not sure about how where to take the ln of the euqaiotn to get rid of the e.

$\displaystyle f(x)= 40+30(2-e^{(-0.2x)}) $

Could some one walk me through it?