n = R * Fa * Fb * Sun
Where:
n = Minimum number of samples in a year.
R = The number of participating gasoline manufacturing facilities.
Fa = Adjustment factor for the number of extra samples required to compensate for samples that could not be included in the NSTOP (e.g., due to technical or logistical considerations), based on the number of additional samples required during the previous 2 calendar years. Fa must be greater than or equal to 1.1.
Fb = Adjustment factor for the number of samples required to ensure oversight. For purposes of this program, Fb equals 1.25.
Sun = Number of samples required per participating facility per year. For purposes of this program, Sun equals 2.
40 C.F.R. §1090.1450