Answer:
This works out to $14.69.
Step-by-step explanation:
C = 0.23m + 0.89 is measured in dollars. $0.89 is the up-front cost, which happens to be the y-intercept. $0.23/min is the unit rate: cost per minute.
Recalling that 1 hour = 60 minutes,
write C(60 min) = $0.89 + ($0.23/min)(60 min)
This works out to $14.69.