A, B, D, and E are correct.
What makes these a function and the others not is that for each x value, there is only one y value. For C, for example, there are multiple y values for the x value of -2. The same goes for F.
The student went wrong in step three. the solutions should have been -3 and 5
Answer:
The number of calculators is 4871
Step-by-step explanation:
If we integrate dx/dt we get x, which is the number of calculators. To find the number of calculators between the beginning of third week to the end of fourth week (the beginning of fifth week), this integration must be evaluated at t between 3 and 5.

the result of the integration is:
to be evaluated between 3 and 5, which is:

So first thing you need to understand is that ABC and AFE are congruent triangles. This means we can find the other angles, based on ABC:
Angle FAE = 26.56505118 degrees
Angle AEF = 63.43494882 degrees
Angles ECD and DEC are both 45 degrees
Now, we can find the angles in ACE:
AEC = 71.56505118 degrees
ECA = 71.56505118 degrees
CAE = 36.86989764 degrees