Lorenzo and neha are 13-year-old twins who are fighting over how to spend a $200 gift certificate they jointly won in a raffle. the gift certificate is for a store that sells mp3 players. there are three kinds of mp3 players available: one that costs $150, one that costs $100, and one that costs $50. each twin wants his or her own mp3 player. both twins greatly prefer the $100 player to the $50 player, but they only slightly prefer the $150 player to the $100 player. the gift certificate can be used only once, regardless of whether or not the full $200 value is redeemed.

suppose their mother intervenes and uses the gift certificate to purchase each twin the $50 player. this outcome is (iffecient/ inefficient) because