The graph represents the cost of a subscription to a newspaper. A 2 column table with 6 rows. The first column, x, has the entries, negative 4, 0, 2, 4. The second column, f(x) has the entries, negative 17.2, negative 13.6, negative 10, negative 6.4, negative 2.8. A 2 column table with 6 rows. The first column, x, has the entries, negative 4, 0, 2, 4. The second column, has the entries, negative 17.2, negative 4, negative 4, negative 4, negative 4. A coordinate plane showing Ferry Ride Cost with Number of Persons on the x-axis and Total Cost in dollars on the y-axis with a line passing through points at (1, 2) and (5, 8).
What is the constant of variation for the subscription cost based on the number of weeks?

$1.50
$7.50
$15.00
$30.00