The figure shows a graph that compares the future values, at 9% compounded monthly, of an annuity of $50 per month and one of $60 per month.
(a) Decide which graph corresponds to which annuity.
(b) Use the graph to estimate (to the nearest 10 months) how long it will be before the larger annuity is $10,000 more than the smaller one.

2$ 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10,000 time 50 150 250 350 Months %24 Dollars