When total utility starts to decrease, each additional song hurts MORE than the previous song.
The answer is John should continue to fix the machine himself.
The answer is $100. The consumer surplus is $100 because that is the difference between what Anna has set as her ceiling for the purchase of the bicycle, $500, and then subtracted by the amount that she actually does pay, $400, that difference is what is referred to as consumer surplus. What the consumer is mentally committed to paying minus what the consumer actually pays.
