kindly answer it in details

4 Example

(a)A agrees with B to sell 100 bags of wheat at Rs. 150 per bag. However before delivery, government bans private trade in wheat.

5 Example

(a)M, a professional shoe shiner starts polishing the shoes of W without being asked to do so, and W allows him to do so and W is under obligation to pay M.

6 Examples

(a)A promises B to pay C a sum of Rs. 1000. The person who can demand performance is B and not C. if A does not pay amount to C, C cannot take any action against A. it is only B who can take action against A. On the death of B, B's legal representatives can only demand performance.