The function is graphed as shown below
Part A:
We use the formula
to find the vertex of the function. A quadratic function of the form of 
and equating this form to the given function 
, we have
and 
.
Substituting
and 
into the vertex formula, we have
, as shown in the graph
This calculation means that the highest profit is achieved when the number of photo printed equals to ten photos
Part B:
We can find solution to this equation by factorising
and 
, as shown in the graph
The two values means that the company makes no profit when they either produce 5 or 15 photos
Part A:
We use the formula
Substituting
This calculation means that the highest profit is achieved when the number of photo printed equals to ten photos
Part B:
We can find solution to this equation by factorising
The two values means that the company makes no profit when they either produce 5 or 15 photos