Common mistakes, Mutual mistakes and Unilateral Mistakes in Contract?

(1). Common Mistake arises where both parties to an agreement are under a misunderstanding. That is, a single mistake shared by both parties. In this mistake there is a full consensus ad idem and the mistake renders a contract void only if it robs it of all substance. 

2). Mutual Mistake arise where each party misunderstands the other, note that; in this mistake there no real consensus ad idem,but the contract is never the less valid only if once interpretation of what was agreed can be deduced from the parties’ words and conduct. Otherwise the mistake is operative and the contract is void. 

3). Unilateral Mistake arises only when one party to a contract is under misunderstanding. It makes the contract void if it relates to the fundamental nature of the offer and the other party new or ought to have known of it.