Sale agreement vs. sale deed and tax implications

A and B entered into a sale agreement for 100000/- (say) stating that A will sell the property to B or a third party mentioned by B on the receipt of the amount mentioned. Subsequently after the receipt of 100000/- A transferred the property to C (a third party) mentioned by B. The sale deed is registered for a sum of Rs.80000/- the question is where will B stands in the entire transaction ?? and what will be the sale consideration for A??