Half the members of a fishing tribe catch 4 fish per day and half catch 9 fish per day. A group of 10 members could build a boat for another tribe in 1 day and receive a payment of 45 fish for the boat.

a. Suppose the boat builders are drawn at random from the tribe. From thetribe's perspective, what is the expected cost of building theboat?

b. Now supposing that members are selected based on opportunitycost, the minimum cost that the boat could be built for is ( ) fish ?