Lets assume John bought the laptop for Rs.100
He then sells it to Mark at a loss of 20%⇒ Rs.80,
Who consequently sells it to Kevin at a profit of 25%⇒ Rs.100
Then, Kevin sells it back to Mark for Rs. 90 (Rs.4.50 for every Rs. 5 that he had paid initially), so he suffers a loss of Rs.10
Therefore, for Rs. 100 there is a loss of Rs.10,
Then for Rs. 1,75,000 there will be a loss of Rs. 17,500.