If you are looking for the equation of the line,
Use Point Slope Form

y-4 = 3(x-1)
y-4 = 3x-3
y = 3x + 1
-- Find any point where y=4
-- Find another point where y=4
-- With your ruler, draw a line between the two points.
You have a horizontal line, and every point on it has y=4 no matter what 'x' is.
The equation for every straight line is [ y = mx+b ].
This is the line where (m = 0) and (b = 4).
Divide it into two squares.
The first square is just (1)1, which equals 1 cm^2, and add that to the second square, which is just (2)2, which equals 4, so 1+4=5 cm^2.
Substitute the number for the appropriate variables and solve
(ab)^2
(4×3)^2
(12)^2
12×12
144
Your answer is B.144