Answer :
ANSWER
The cost increases $4 for every additional square foot being painted
OPTION A
STEP-BY-STEP EXPLANATION:
To solve this particular problem, we need to find the slope/gradient of the line and the y-intercept on the y-axis.
To do this, we need to follow the steps below
Step 1: Pick any two points on the graph to calculate the slope
The points are (120, 480) and (360, 1440)
Let x1 = 120, y1 = 480, x2 = 360, y2 = 1440
[tex]\begin{gathered} \text{Slope = }\frac{rise}{\text{run}} \\ \text{rise = y2 - y1} \\ \text{run = x2 - x1} \\ \text{Slope = }\frac{y2\text{ - y1}}{x2\text{ - x1}} \end{gathered}[/tex]Substitute the above data into the slope formula
[tex]\begin{gathered} \text{Slope = }\frac{1440\text{ - 480}}{360\text{ -120}} \\ \text{Slope = }\frac{960}{240} \\ \text{Slope = 4} \end{gathered}[/tex]Hence, the slope of the line is 4
Step 2: Find the slope-intercept form
Recall, y = mx + b
Where m is the slope of the line
b is the intercept of the y-axis
[tex](y\text{ - y1) = m(x - x1)}[/tex]m = 4, x1 = 120, and y1 = 480
Substitute the above data into the slope-intercept formula
[tex]\begin{gathered} (y\text{ - 480) = 4(x - 120)} \\ \text{open the parentheses} \\ y\text{ - 480 = 4x - 480} \\ \text{Add 480 to the both sides} \\ y\text{ - 480 + 480 = 4x - 480 + 480} \\ y\text{ =4x+ 0} \\ y\text{ = 4x} \end{gathered}[/tex]Hence, the cost increases $4 for every additional square foot being painted