Answer:
1) Second option:

2) Third option: $14,500
Explanation:
1) The equation of the line in Slope-intercept form is:

Where m is the slope and b is the y-intercept.
You know the point (20,7) of the line and you can observe in the graph that the y-intercept is:

Then, you can substitute these values into the equation

and solve for the slope "m":

Therefore, the equation of this line is:

2) To calculate the total cost of producing 50 engines, you need to substitute
into the equation of the line
. Then you get:



Since the y-axis represents the total cost "y" in thousands of dollar, then the total cost of producing 50 engines is:
$14,500