A cell phone plan costs $21.80 per month for 500 minutes of talk time. It costs an additional $0.04 per minute for each minute over 500 minutes. To get e-mail access, it costs 30% of the price for 500 minutes of talk time. Your bill, which includes e-mail, is the same each month for 5 months. The total cost for all 5 months is $159.70. Write and solve an equation to find the number of minutes of talk time you use each month.