The cost of a long-distance phone call from Boston to London is defined by f(t) = 0.85(t -1) + 1.50, where the cost is $1.50 for the first minute and $0.85 for each additional minute. The cost of a five-minute phone call is
$ 3.40
$ 4.90
$ 5.75
$ 7.50
$ 9.60