A cell phone company charges $39.99 flat fee each month, plus $0.05per minute. If m represents the number of minutes used in a month, which expression can be used to calculate a monthly payment?

Diane’s bank is offering 5% interest, compounded monthly. if diane invests $10,500 and wants $20,000 when she withdrawals, how long should she keep her money in for? round to the nearest tenth of a year.