A cell phone plan costs ​$29.80 per month for 800 minutes of talk time. It costs an additional ​$0.07 per minute for each minute over 800 minutes. To get​ e-mail access, it costs 20​% of the price for 800 minutes of talk time. Your​ bill, which includes​ e-mail, is the same each month for 8 months. The total cost for all 8 months is ​$320.80. Write and solve an equation to find the number of minutes of talk time you use each month.