Alaptop has a listed price of a laptop that has a listed price of $715.99 before tax at the sales tax rate is 7.75% find the total cost of the laptop with sales tax included round your answer to the nearest cent as necessary

An 80:1 scale means that for every unit on a diagram, there are 80 units in the real world.  So, this means that the floor plan is (80x4) x (80x5) cm, which equals 320 x 400 cm. 
If you want to further simplify your answer, this translates to 3.2 meters x 4 meters