Part a.
The total area is the area of the rectangle, that is,
which is the wide times the lenght. So, the total area is
Part b.
We need to find the dark gray area and the light gray area separately. The dark gray area is
and the light gray area is
In the first case, Mila has 70 dark gray tiles, since each tile is 1 square foot, she has 70 square foot of tiles then, in this particular case, her plan will work because the dark area is 40 square feet. However, in the light gray case, she only has 30 tiles or, equivalently, 30 square foot of tiles but the light gray area is 32 square feet, so she will need 2 more tiles. Therefore, her plan doesnt quite work.