A cell phone plan costs $19.70 per month for 600 minutes of talk time. It costs an additional $0.07 per minute for each minute over 600 minutes. To get e-mail access, it costs 30% of the price for 600 minutes of talk time. Your bill, which includes e-mail, is the same each month for 7 months. The total cost for all 7 months is $221.90. Write and solve an equation to find the number of minutes of talk time you use each month.​