Answer
The emf of the Emf device is $~48~V$
Work Step by Step
In part (a), we found that the potential difference between A and B is $~~50~V$
We can find the potential difference $\Delta V$ across the $2.0~\Omega$ resistor:
$\Delta V = i~R = (1.0~A)(2.0~\Omega) = 2.0~V$
Therefore, the potential difference across the Emf must be $48~V$
The emf of the Emf device is $~48~V$
