NI R Ltd manufactures three products, the selling price and cost details of which are given below. Product P Product Product R et of E 150 190 190 Selling price per unit Costs per unit Direct materials (5/kg) Direct labour (4/hour) Variable overhead Fixed overhead In a period when direct materials are restricted in supply, and are thus a scarce resource, the products with the highest and lowest contribution per unit of scarce resource are: Select one: a. Highest: P - Lowest: R b. Highest: Q - Lowest: R c. Highest: R - Lowest:P d. Highest: R - Lowest