13. Notwithstanding anything contained in section 56 of the Contract Act, a contract is not wholly impossible of performance because a portion of its subject-matter, existing at its date, has ceased to exist at the time of the performance.Illustrations (a) A contracts to sell a house to B for a lakh of taka. The day after the contract is made the house is destroyed by a cyclone. B may be compelled to perform his part of the contract by paying the purchase-money. (b) In consideration of a sum of money payable by B, A contracts to grant an annuity to B for B's life. The day after the contract has been made, B is thrown from his horse and killed. B's representative may be compelled to pay the purchase-money.