An 8-minute call would supposedly cost 40 cents, as shown below.
[tex]\dfrac{5\,\textrm{cents}}{\textrm{min}} \cdot 8 \, \textrm{min} = 40 \, \textrm{cents}[/tex]
However, the information in the problem states that the minimum charge for a call is 70 cents. Since 40 cents is less than 70 cents, we will have to take the 70 cent charge, meaning the phone call costs 70 cents.
