1.- A certain amount of money is deposited in an account, in which the interest is applied continuously. If the principal doubles after 6 years, what is the interest rate?

2 .. How much money should be invested today at an annual interest rate of 7% continually capitalized, so that within 15 years it is 90% of $ 30,000?

3. - If $ 8,500 are invested at an annual 6% compounded with semiannual capitalization, the amount at 4 years is: