As a woman carries her suitcase up a flight of stairs, she does work against gravity. if the mass of her suitcase is 25 kg and the flight of stairs is 15 m tall, how much work does she perform by carrying her suitcase?

Gravitational potential energy above a reference level is  M G H .

In this story,
-- M = 25kg
-- H = 15m
and if the story takes place on Earth, then
-- G = about 9.8m/s².

     PE = (M) (G) (H) = (25) (15) (9.8) = 3,675 joules .

That's the gravitational potential energy acquired by the suitcase
in the process of being lifted 15 meters straight up.

Sadly, human physical effort is far from 100% efficient, and the woman in
the story has to expend a lot more energy than that just to lift the suitcase
up the stairs.  AND PLUS don't forget that she also has to come up with
enough additional energy to increase the potential energy of her own mass,
no matter how dainty it may be, by 15 vertical meters' worth.

Now 25 kg = about 55 pounds,
and 15 meters = about 50 feet, or something like 4 to 5 stories

You can be sure that some beads of glow highlight her forehead
by the time she's done with this job.