Please help with this calculus question

For a long-distance phone call, a hotel charges $9.09 for the rst minute and $0.69 for each additional minute or fraction thereof. A formula for the cost is given below, where t is the time in minutes. (Note: [[x]] = greatest integer n such that n s x. For example [[3.2]] = 3 and [[1.6]] = 2.) C(t) = 9.09 0.69[[ (t 1)]] (5) Use a graphing utility to graph the cost function for 0