8. For each of the following situations, determine whether adverse selection, moral hazard, or the principal-agent problem is at work.

a. You decide to buy a scalped ticket before a concert, but you are not entirely sure the ticket is legitimate.

b. A contractor takes a long time to finish the construction work he promised after you gave him his final payment.

c. You hire a neighborhood teenager to mow your grass once a week over the summer while you are traveling. The teenager mows your grass every three weeks instead.