A retailer offers a discount scheme 'Buy 3 get 1 free'. Every item costs ₹3,000. He gave a additional discount of 20% on the total bill to his relative. If his relative takes home 4 items, then how much would he have paid?

A company considers hiring an extra machine for $150 per day to produce additional units. If the additional throughput contribution generated from producing these units on the machine is $390, by how much will total profit increase?

If the cost price of an article is 85 times its selling price, what is the loss percentage?