In triangle ABC, angle ABC=90 degrees

AB=5.3, correct to 2 sig figs

BC=4.8cm, correct to 2 sig figs

The base, AB of the triangle is horizontal

Calculate the lower and upper bounds of the line AC.

Never encountered before. I don't even know how to calculate the gradient. Or what the gradient is, only ever seen it in graphs. Is it a vector of some sort?

Full workings if possible please.