Using x hours of skilled labor and y hours of unskilled labo

Using x hours of skilled labor and y hours of unskilled labor, a manufacturer can produce Q(x,y)=80xy^(1/2) units each week. Currently 100 hours of skilled labor and 9 hours of unskilled labor are being used. Suppose the manufacturer reduces the skilled labor level by 3 hours and increases the unskilled labor by 6. Use calculus to determine the approximate effect of these changes on production.
Production changes by approximately????