A car owner buys petrol at Rs. 7.50 Rs. 8.00 and Rs. 8.50 per litre for the 3 successive years. If he spends Rs. 4000 each year, then the average cost per litre of petrol is

Question

$\begin {array} {1 1} (A)\;Rs. 8 & \quad (B)\;Rs.8.25 \\ (C)\;Rs. 7.98 & \quad (D)\;None \: of \: these \end {array}$