Answer:
Benny will hire more candy sellers.
Explanation:
Benny is currently making a $13 per hour profit for every candy seller that he hires: $20 (marginal product) - $7 (salary) = $13
If the price of candy bars increases to $2 and the quantity demanded remains unchanged, Benny will be making a $33 profit for every candy seller: $40 (marginal product) - $7 (salary) = $33
So Benny will be highly motivated to hire more candy sellers in order to keep increasing his profit.