Answer:
i believe the answer is $0.22 per pound.
Step-by-step explanation:
1. Given (12+3)x, we can sum the numbers in the parenthesis to get 15x
2. Given 12x+3x, we can factor x to get (12+3)x and get the same as 1.
3. Given (12+3x)x, we have to distribute the x and we have 
4. This expression is already simplified.
Vertex = 1,4
range = ( infinity, 4)
maximum
The answer to your question is D