John is making a tent for his next camping trip out of waterproof material. He is going to use two different colors for the tent and needs to know how many square yards of material he will need for the lateral portion of the tent. The equilateral triangular-shaped opening of the tent, or base, has side lengths of 3 yards, and the tent will be 6 yards long. How many square yards of material does John need for the lateral portion of the tent? A. 15 square yards B. 63 square yards C. 54 square yards D. 36 square yards