B and C only

Week 11 - Assessment Question Moderna, the US pharmaceutical company has seen their share price grow from 52.18 USD in May 2020, to 161.38 USD in May 2021. Moderna's development of an effective MRNA vaccine, which combats Covid-19, has had a significant effect on its share price. Taking the above into account, answer the following questions: a) Define the term externality as it is used in Microeconomics. b) Is Moderna's development of a vaccine considered a negative or positive externality? c) How can government's move closer to closing the externality gap (private vs social)? d) Without government intervention, will the market produce more or less than the socially optimal amount of Covid-19 vaccines