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