A person buys a phone for ​$81 and signs up for a​ single-line phone plan with 2000 monthly anytime minutes. The plan costs ​$119.92 per month. Write an equation that can be used to determine the total​ cost, C(t), of this phone plan for t months.​ Then, find the cost for 23 ​months, assuming that the number of minutes the person uses does not exceed 2000 per month.