A company produces products at 2 plants each of which have a capacity of producing 75 units. 50 units of each product must be shipped to each of three customers. We know the cost of shipping a unit of the product from each plant to each customer. Our goal is to minimize the total cost of shipping the needed units to the customers. If we use the Excel Solver to try and minimize the total cost of meeting customer demand we will need how many variable cells?

a. 2

b. 6

c. 3

d. none of the above