A shopkeeper sells two articles at ₹840 each. He earns a 20% profit on the first article and incurs a 20% loss on the second article. Determine the net profit or loss percentage he incurs.

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?