Answer:
25
Step-by-step explanation:
From the given information;
Numbers of posters that can be printed in an hour = no of impression/hour × no of plate utilized in each impression.
= 1000x
Thus, the required number of hours it will take can be computed as:

cost per hour = 125
If each plate costs $20 to make, then the total number of plate will equal to 40x
∴
The total cost can be computed as:


At C'(x) = 0




x = 25


where; x = 25

C''(x) = 1.6
Thus, at x = 25, C'' > 0
As such, to minimize the cost, the printer needs to make 25 metal plates.
We know that the equation of the line is in the form
. To find b, we can use the fact that (6,-5) lies on the line, meaning that both sides of the equation are equal when x=6 and y=-5.

Hence, the equation of the line is
, and its graph looks something like follows.
The first one is, because when you have an exponent multiplied by an exponent, you keep the base and just multiply the exponents when you do this, you get 7^-6. When you have a negative exponent you simply put the exponential answer as if it were positive on the denominator of a fraction with the numerator of 1.