Answer: [tex]4[/tex] pairs
Step-by-step explanation:
Given
Profit on selling 'x' pairs of shoes is [tex]P(x)=-4x^2+32x-39[/tex]
Find the derivative of the function to find out the critical points
[tex]\Rightarrow -8x+32=0\\\Rightarrow x=4[/tex]
Thus, for 4 pair of shoes profit is maximize.