Answer : Option D

Explanation :

Let the commodity P costs 40 paise more than the commodity Q after n years
Price of the commodity P in 2001 = Rs.4.20
Since the price of the commodity P increases by Rs 0.40 every year,
Price of the commodity P after n years from 2001 = Rs.4.20 + (n × .40)
Price of the commodity Q in 2001 = Rs.6.30
Since the price of the commodity Q increases by Rs 0.15 every year,
price of the commodity Q after n years from 2001 = Rs.6.30 + (n × .15)
Since the commodity P costs Rs. 0.40 more that the commodity Q after n years from 2001,
4.20 + (n × .40) = 6.30 + (n × .15) + 0.40
=> (40n - .15n) = 6.30 - 4.20 + 0.40 = 2.5
=> .25n = 2.5

$MF#%\Rightarrow n = \dfrac{2.5}{.25} = \dfrac{250}{25} = 10$MF#%