Answer: c = 33 is y-intercept in the function f(x)=4x+33.
Explanation:
Since we have given that
At 6 A.M, there were 57 people and
At 8 A.M., there were 65 people.
So, to get the rate of change we will find the slope using these data as coordinates i.e.

So,

Now, equation of line using these 2 points is given by:

which in general is the form of slope intercept form i.e.

So, here c=33 which represents the y-intercept .