Few Simple Economics question

a) What is Hidden Knowledge? Give an example of hidden knowledge. Why do hidden knowledge issues break a simple market?

b)One of the BC government's responses to COVID was to create rent freeze (i.e. for any existing tenant, the price of rent cannot increase if you are currently a renter) that has been extended until July 9th, 2021. Make a graph illustrating how this policy would work and explain what economist call this type of policy. Be sure to talk about the consequences of social welfare. Use this example to illustrate/explain the idea of government failure