Miles is three years old and his grandparents have given him money to spend at the toy store as a birthday present. Miles' number one favorite thing to play with is building blocks. Assume that Miles' utility will increase by 100 units if he purchases a new set of building blocks and and it will cost him $50. His second favorite thing to play with is fire trucks. Fire trucks cost $20 and each new fire truck improves Miles' utility by 80 units. His third favorite toy is trains. Trains improve his utility by 15 units and cost $5 each. Miles does not have to spend all of his money at once, but wants to get as much happiness as possible from his money. If Miles buys only one toy, which should he buy to maximize his utility? building blocks a fire truck a train