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.