The correct option is A 1672 J
Given
Heat supplied (H)=400 calories
Let the work done in supplying heat to the system be W (say)
We know that W=JH, where, J is the mechanical equivalent of heat which has a value 4.18 joules /calorie
∴ W=4.18×400=1672 J
Thus, option (a) is the correct answer.