A, B and C rent a pasture. If A puts 10 oxen for 7 months, B puts 12 oxen for 5 months and C puts 15 oxen for 3 months for grazing and the rent of the pasture is Rs. 140, then how much amount should C pay as his share of rent?  Choose the most appropriate option
A) 35 B) 45 C) 25 D) 36 E) 55

Rationale: "a : b : c = 10 × 7 : 12 × 5 : 15 × 3 = 2 × 7 : 12 × 1 : 3 × 3 = 14 : 12 : 9 amount that c should pay = 140 × 9 / 35 = 4 × 9 = 36 answer is d"
Answer: D