The Brainliest Answer!
The work done on the box by the man is zero as the force acting on the box is at an angle of 90,, and such a force means 0 or no work. If it was said that 'what is the work done by the man on climbing the stairs' then it would be positive as the man is gaining height thereby gaining potential energy. But in this case the work done is ZERO.
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Thanku... does that mean my answer is right?