When a resistor of $11 \; \Omega$ is connected in series with an electric cell, the current flowing in it is $0.5 \;A$. Instead, when a resistor of $5 \Omega$ is connected to the same electric cell in series, the current increases by $0.4 \;A$. The internal resistance of the cell is :

Question

( A ) $3.5 \; \Omega$
( B ) $1.5 \; \Omega$
( C ) $2.5 \; \Omega$
( D ) $2 \; \Omega$