Calculate the areas and densities. Report the answers in the correct units.

a. the area of a rectangle with sides measuring 3 x 10^1 cm and 3 x 10^-2 cm

b. the area of a rectangle with sides measuring 1 x 10^3 cm and 5 x 10^-1 cm

c. the density of a substance having a mass of 9 x 10^5 g and a volume of 3 x 10^-1 cm3

d. the density of a substance having a mass of 4 x 10^-3 g and a volume of 2 x 10^-2 cm3