How to calculate the power of man when he runs long flight of stairs physics numerical

A 70kg man runs up a long flight of stairs in 4 s. The vertical height of the stairs is 4.5m. Calculate his power
This is simple physics numerical from course book of chapter 4 work and Energy
tags
#power #work#energy #physics

[@user-je9lf1ly3b]

He go upstairs against the gravity so why gravitational acceleration don't take negative.

[@TechType0]

Since power is a scalar quantity, we usually don't consider the negative sign in this context.