Answer : Option A

Explanation :

Let the C.P of an article is 100.
ATQ, S.P will be 110...................................................... (i)
If he has purchased it at 20% less, the new C.P = 100 - 20= 80

If the C.P is 80, then he earns a profit of 40% and sells the article at Rs 10 more than the previous price.
So, when he earns 40%, the new C.P = (40/100) * 80 = 32

That means if the C.P = 80, the S.P = 80+32 = 112............................ (ii)

Compare equation 1 and 2, and we get the difference between S.P is = 2
But ATQ, it should be 10, i.e., multiple of 5
So, we need to multiply the actual value with 5 then we get actual cost price.

Hence, the C.P of the article is = 100 * 5 = 500