Suppose that an investment of $4200 earns an interest rate 7% per year compounded continuously. Find the time it takes this investment to double as follows:
Write an equation by using the given information in the compound continuous interest formula.
Hint: What would the balance be if the investment doubled.
Solve this equation and answer the question: What is the amount of time it takes this investment to double. Round answer to one decimal digits and include units.