3. When a party to the contract prevents the other from performing the promises the contract becomes voidable on the option of the party so prevented and he is entitled to compensation from the other party for any loss which he may sustain in consequence of the non-performance of the contract. (Sec. 53)
4. According to Sec. 54, when a contract consists of such reciprocal promises that one of them cannot be performed till the other has been performed and the promisor of the promise last mentioned, fails to perform it, he cannot claim the performance of the reciprocal promise.
In such a case, he must make compensation to the other party for any loss which such other party may sustain by the non-performance of the contract.
5. If time is the essence in a mutual contract and the promise is not performed at the time prescribed by the promisee, the other party may assume that the contract is terminated. (Sec. 55)
6. Any reciprocal agreement to do an act, performance of which is impossible since beginning, is void under Sec. 56.
7. Sec. 57 says, when a contract consists of two parts-one part is legal and the other illegal and the legal part is separate from the illegal one, the first act of promise is a contract, and therefore, enforceable, but the second is void agreement being illegal.
8. In the case of alternate promise, one branch of it being legal and the other illegal, the legal branch alone can be enforced. (Sec. 58)