Answer:
The car is going up at a speed of 22.5 mph 
Step-by-step explanation:
In this question, we are asked to calculate the speed of a moving car which started moving at an initial velocity for a specific period of time. 
To calculate this, we use one of the basic equations of motion; 
v = u + at
Where v is the final velocity, u is the initial velocity and t is the time 
From the question, we can identify the parameters as follows; 
v = ?
u = 10mph 
a = 2.5t mph per second for 5 seconds. 
Hence a here would be 2.5 * 5 = 12.5
Now, let’s put these values in the equation 
v = 10 + 12.5 
v = 22.5 mph