50*10 = 500
68*5 = 340
840/15 = 56
If 10 litres of an oil of Rs.50 per litres be mixed with 5 litres of another oil of Rs.68 per litre then what is the rate of mixed oil per litre?

(A) Rs.49.17
(B) Rs.51.03
(C) Rs.56
(D) Rs.55.33
(E) None of the above