I think this algebra..

I have been giving alot of questions to do with upper and lower bounds, an example is:

Two sides of a rectangle were measured to the nearest mm, as 4.6 cm and 7.9 cm.

a) Find the least and greatest possible values of the perimeter.

b) Find the least and greatest possible values of the area.

It's probably simple but i havent done perimeter versions yet.

Thanks all!