Coulomb's constant, 8,987,551,787 N-m^2/C^2, is used to calculate the electric force
between two stationary charged particles. What is the correct form of this in
scientific notation with 2 significant figures?
a. 8.9x10^-9
b. 90.0x10^8
c. 0.8900x10^-8
d. 8.9x10^9