An elevator ascends vertically at constant speed. Its floor exerts an upward tension T on the cabin that is equal in magnitude to its weight W acting downward. For a vertical upward displacement of 2m, what are the signs of the work done by the tension and by the weight, respectively?
a) Both zero
b) Tension: negative; Weight: positive
c) Tension: positive; Weight: negative
d) Tension: positive; Weight: zero