Given below is a statement of legal principle followed by factual situation. Apply the principle to the facts and select the most appropriate answer.
Principle: Where both parties to an agreement are under a mistake as to matter of fact essential to the agreement, the agreement is void.
A had a piece of land. He believed that the value of the land was Rs.1,000 per square foot. B knew that the value of the land was infact Rs.1,500 per square foot. However, he did not inform A and purchased the land at Rs.1,000.