The Gillian restaurant located in Vaudreuil has a creamery that prepares its desserts according to the tastes of its customers. The two main products are ice cream and frozen yogurt, to which customer-specified additions are mixed. To stock up, the restaurant places an order with its ice cream and frozen yogurt suppliers each week. The store has enough freezer space to store 115 gallons of both products. A gallon of frozen yogurt costs $0.75 and a gallon of ice cream costs $1.00. The restaurant plans to budget $90 each week for these items. The manager estimates that each week the restaurant sells at least twice as much ice cream as frozen yogurt. The profit per gallon of ice cream is $4.00 and the profit per gallon of yogurt is $3.60.

(a) Algebraically formulate a linear programming model to represent this problem. Define decision variables, objective function and constraints.