$5,000 is invested in an account bearing 10% interest compounded continuously. The amount of time it takes for the money to grow by a factor of x is...

$5,000 is invested in an account bearing 10% interest compounded continuously. The amount of time it takes for the money to grow by a factor of x is given by t = f(x)=10ln (x) . (For example, the amount of time required for the investment to double is f(2) = 10ln (2).) How long will it take the balance in the account to reach $7,500? Find a formula for the inverse function. Evaluate f-1(8) and explain what this tells you in practical terms.