Answer:
The total cost producing 1 camera case is:
$ 11
Explanation:
Let the quadratic function be:

Now, c(3)=45
This means:

c(7)=257
This means that:

and c(12)=792
This imply:

On subtracting first equation from second we get:

and on subtracting second equation from third we get:

Now on multiplying equation (4) by 5 and equation (5) by 4 and subtracting both equation we get:
a=6
Putting value of a in equation (4) we get:
b= -7
and putting the value of a and b in equation (1) we get:
c=12
Hence, the cost function is:

Now, the cost of producing 1 camera will be the value of c(x) when x=1
i.e.

Hence, the answer is:
$ 11