120kg of an alloy A is mixed with 180 kg of alloy B. If alloy A has lead and tin in the ratio 2:3 and alloy B has tin and copper in the ratio 3:5, then the amount of tin in the new alloy is?	Choose the correct answer
A) 100.6 kg	B) 120.3 kg	C) 139.5 kg	D) 140.8 kg	E) 114.5 kg

Rationale: "quantity of tin in 120 kg of a = 120 * 3 / 5 = 72 kg quantity of tin in 180 kg of b = 180 * 3 / 8 = 67.5 kg quantity of tin in the new alloy = 72 + 67.5 = 139.5 kg answer is c"
Answer: C