How many square feet does a 4.0 ton air conditioner unit cover?

1800 to 2500 depending on many factors (area of country, ambient humidity & temp, air flow and other factors ). Best to consult your local HVAC contractor.

This really depends on your heat loss such as how well insulated walls and windows are. But you should be good up to at least 3000 sq ft

A square can be built to cover as many or as few square feet as you want it to cover. This may be one reason that squares have the reputation of being so useful and elegant. If one day you should...

40' x 40' (1,600 square feet) = 177.77 square yards.

800 to 1000 sq ft