You have plated 1 mL of a sample culture diluted 1:1x10⁶ and counted 89 colonies. What is the cell density of the sample culture in CFU/mL?
a) 1.78 x 10⁸ CFU/mL
b) 1.12 x 10⁷ CFU/mL
c) 8.9 x 10⁴ CFU/mL
d) 4.45 x 10⁴ CFU/mL