A square loop with 2.0 m sides is perpendicular to a uniform magnetic field, with half the area of the loop in the field is shown in figure. The loop contains a 20.0 V battery with negligible internal resistance. If the magnitude of the field varies with time according to B = 0.042-0.871, with B in tesia and t in second. The net emf of the circuit is:

• A. \[20.0\,V\]
• B. \[18.26\,V\]
• C. \[21.74\,V\]
• D. None of these