Correct Answer - D
Equivalent emf of two batteires `epsilon_1` and `epsilon_2` is `epsilon=(epsilon_1//r_1
+epsilon_2//r_2)/(1//r_1+1//r_2)=((2//2)+(4//6))/((1//2)+(1//6))`
`2.5V`
Now, `V_(AN)=epsilon`
`:. I_(AN)=(R_(AN))=epsilon`
or `((12)/(4+4xx4))(4)(l)=2.5`
Solving this equation we get
`l=2.5/24m`