A shopkeeper sells 400 metres of cloth for $18000 at a loss of Rs.5 per metre. Find his cost price for one metre of cloth? Pick.
A) $ 20  B) $ 43  C) $ 50  D) $ 70  E) $ 40

Rationale: "c $ 50 sp per metre = 18000 / 400 = $ 45 loss per metre = $ 5 cp per metre = 45 + 5 = $ 50"
Answer: C