Cheng likes a modern lawn sculpture made of four identical solid right pyramids with square bases. he decides to create an exact copy of the sculpture, so he needs to know what volume of sculpting material to purchase. he measures each edge of each base to be 2 feet. the height of the whole sculpture is 6 feet. what is the volume of material he must purchase? 2 ft3 4 ft3 6 ft3 8 ft3