Use the model =APert or =AP+1rnnt, where A is the future value of P dollars invested at interest rate r compounded continuously or n times per year for t years. If $15,000 is invested in an account earning 7.5% interest compounded continuously, determine how long it will take the money to double. Round up to the nearest year.

Abank manager wants to encourage new customers to open accounts with principals of at least $2,500. he decides to make a poster advertising a simple interest rate of 3%. what must the principal be if the bank manager also wants to advertise that one can earn $10 the first month? can the poster correctly say, "open an account of $2 comma 500 and earn at least $10 interest in 1 month! "?