Question: If after 200 microliters of a 10-4 dilution (10 exp. -4) of a broth on an agar plate grows 100 colonies, the estimated number of colony forming units per mL of broth is: 
 Options:  <1> 0.2 x 104 <2> 2 x 106 <3> 5 x 104 <4> 5 x 105 <5> 5 x 106
5