There are 58 – 8 = 50 returns with no errors.
There are 58 * 57 * 56 / 1 * 2 * 3 = 1110816 possible sets
of 3 returns that the auditor could pick.
Of those 50 * 49 * 48 / 1 * 2 * 3 = 705600 are sets of 3
returns with no errors,.
The number of possible sets of 3 returns with no errors as a
fraction of the number of possible sets of 3 returns available for auditing is:
50 x 49 x 48 / 58 x 57 x 56 = about .647
So the probability is computed is 64.7/100 = 64.7%
