The answer is you would sell the product for $15 dollars. you would make a profit of $10
Your a wierd person you already know its 4
Steps to solve:
f(x) = 1/2(4 - x) when x = 2
~Substitute
f(2) = 1/2(4 - 2)
~Subtract whats in parenthesis
f(2) = 1/2(2)
~Multiply
f(2) = 1
Best of Luck!