The explanatory variable is placed on the x-axis and the response variable is placed on the y-axis.
Answer:
<em>The speed of the plane after it decelerates is 50 m/s</em>
Explanation:
<u>Motion with Constant Acceleration</u>
When an object gains or losses velocity in time, it acquires acceleration. If this value is constant, we can calculate the final velocity (or speed in scalar terms) as:

Where vf is the final speed, vo is the initial speed, a is the constant acceleration, and t is the time the acceleration is acting.
The plane is originally traveling at vo=80 m/s and it slows down at a constant rate of
during t=120 seconds. Note we have added the negative sign to the acceleration because the plane is slowing down, i.e., the acceleration is against the speed.
Thus, the final speed is:



The speed of the plane after it decelerates is 50 m/s
We can use 3rd equation of motion to find the velocity of the stone just before it strikes the ground.
Height = S = 318 meters
Acceleration = a= 9.8 m/s²
Initial velocity = u = 0
Final velocity = v = ?
According to the 3rd equation of motion:
2aS = v² - u²
2(9.8)(318)=v²
v²=6232.8
⇒
v = 78.95 m/s
So, the velocity rounded of to nearest integer will be 79 meters per second.
Thus, C option is the correct answer