aPlease find the answer and explain why it's right. Thanks!

48. To implement the socially optimal outcome, what should be the contribution of Alice? (a) o (b) 2 4 (d) 6 49. To two fishermen, a codfish swimming in the middle of the ocean is a good that is a rival and excludable. (b) rival and non-excludable. (c) non-rival and excludable. (d) non-rival and non-excludable