The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in
minutes). The remaining credit after 28 minutes of calls is $15.52, and the remaining credit after 39 minutes of calls is
$13.76. What is the remaining credit after 48 minutes of calls?
Remaining
credit
(in dollars)
Calling time
(in minutes)
s
X