So directly the cell density value in a rectangle is:
[tex]5*10^{17} cells/cm^{2}[/tex]
In this exercise, we must first calculate the area of the rectangle, remembering that you need to convert from nm to cm is:
[tex]A=B*H\\A=(0.4*10^{-7})*(0.5*10^{-7})= 2*10^{-15}[/tex]
Next, let's calculate the density from the calculated area:
[tex]\frac{N}{A} = \frac{1000}{2*10^{-15} } = 5*10^{17}[/tex]
In this way, the calculation represents that there is:
[tex]5*10^{17} cells/cm^{2}[/tex]
Learn more: brainly.com/question/18320053