(A) Contract Act (9 of 1872) , S.72— Unjust enrichment - Ingredients. The principle of unjust enrichment requires : first, that the defendant has been 'enriched' by the receipt of a "benefit", secondly, that this enrichment is "at the expense of the plaintiff"; and thirdly; that the retention of the enrichment be unjust. This justifies restitution. Enrichment may take the form of direct advantage to the recipient's wealth such as by the receipt of money or indirect one for instance where inevitable expense has been saved.(Para 11) (B) Contract Act (9 of 1872) , S.72— Money paid under mistake of law - Suit for refund - Limitation - Starting point - @page-SC314Date of judgment of Court declaring law under which payment was made as void. Limitation Act (36 of 1963) , S.17(1)(c), Art.113— F. A. No. 23 of 1966, D/-6-4-1972 (Madh Pra), Reversed. In a suit for refund of money paid by mistake of law, S.72 of the Contract Act is applicable and the period of limitation is three years as prescribed by Art. 113 of the Schedule to the Indian Limitation Act, 1963 and the provisions of S.17(1)(c) of that Act will be applicable so that the period will begin to run from the date of knowledge of the particular law, whereunder the money was paid,....