Amar went to buy a biscuit worth Rs. x. He gave Rs. 10 rupee note to the shopkeeper to buy the biscuit then shopkeeper gave rest of the money in the denominations of 50 paise, 1 rupee, and 2 rupees. If the ratio of the number of coins is 4 : 2 : 1 respectively. Then what is the price of the biscuit?