The profit earned after selling an article for ₹5,600 is the same as the loss incurred after selling the article for ₹2,400. The profit is :

$$Profit = (selling\ price)_1 - cost\ price$$

$$Profit = 5600 - cost\ price$$    Eq.(i)

$$Loss = cost\ price - (selling\ price)_2$$

$$Loss = cost\ price - 2400$$    Eq.(ii)

As per the information given in the question, Eq.(i) = Eq.(ii)

$$5600 - cost\ price = cost\ price - 2400$$

$$5600+2400  = cost\ price +cost\ price$$

$$2\times$$ cost price = 8000

cost price = 4000

Profit = $$\frac{profit}{cost\ price}\times 100$$

= $$\frac{5600 - cost\ price}{cost\ price}\times 100$$

= $$\frac{5600 - 4000}{4000}\times\ 100$$

= $$\frac{1600}{4000}\times\ 100$$

= 40%