4 Long-distance calls from New York to Harare are priced at
85 cents/min off peak and $1.20/min at peak times.
a) Draw, on the same axes, conversion graphs for the two different rates.
b) From your graph estimate the cost of an 8 minute call made off peak.
C) Estimate the cost of the same call made at peak rate.
d) A call is to be made from a telephone box. If the caller has only $4 to
spend, estimate how much more time he can talk for if he rings at off
peak instead of at peak times.