A graph has time (hours) on the x-axis and Total costs (dollars) on the y-axis. Points are at (4, 52), (5, 60), (6, 68) and (7, 76).
The graph shows the charges of an instructor. The instructor charges an initial fee and then an hourly rate for private lessons. Determine the instructor's hourly charge from the graph.

What is the hourly charge?
$1.00
$4.00
$7.00
$8.00