Bruce corporation makes four products in a single facility. these products have the following unit product costs:
products
a b c d
direct materials $ 14.20 $ 10.10 $ 10.90 $ 10.50
direct labor 19.30 27.30 33.50 40.30
variable manufacturing overhead 4.20 2.60 2.50 3.10
fixed manufacturing overhead 26.40 34.70 26.50 37.10
unit product cost $ 64.10 $ 74.70 $ 73.40 $ 91.00

additional data concerning these products are listed below.
products
a b c d
grinding minutes per unit 3.70 5.20 4.20 3.30
selling price per unit $ 76.00 $ 93.40 $ 87.30 $ 104.10
variable selling cost per unit $ 2.10 $ 1.10 $ 3.20 $ 1.50
monthly demand in units 3,900 3,900 2,900 3,100

the grinding machines are potentially the constraint in the production facility. a total of 54,900 minutes are available per month on these machines. direct labor is a variable cost in this company. how many minutes of grinding machine time would be required to satisfy demand for all four products?