Q1.2 BPP F5 Practice & Revision Kit (For exams up to June 2015)

Q1.2 When machine time is a binding constraint on production output, which one of the following will have NO EFFECT on the throughput accounting ratio for a product that the machine is used to manufacture ? A Obtaining a lower purchase price for materials for the product B Reducing factory costs C Reducing the machine time per unit to make the product D Increasing the selling price of the product Answer is C. I don't think it's correct because : reducing the machine time per unit will make throughput per unit of machine time higher and no effect to factory cost per unit of machine time , so TPAR will be higher. How do you think about that ? BPP makes a lot of mistakes in their books lately