The total cost for 8 hours of work is $425.
The total cost for 10 hours of work is $525.
The total amount the plumber earns is made up of a fixed charge and a variable charge. A fixed charge is a charge that remains constant regardless of the number of hours the plumber works. The fixed charge is $25. The variable charge is the charge that increases per hours worked. The variable charge is $50 per hour.
Cost = fixed charge + variable charge
C = $25 + $50h
The total cost for 8 hours
$25 + $50(8)
$25 + $400
= $425.
The total cost for 10 hours
$25 + $50(10)
$25 + $500
$525.