For a group experiment, your science class measured the fine-particulate concentrations in the air at random places around campus, and estimated a sample average of 22 μg/m3 (micrograms per cubic meter). if 144 readings were taken, and the standard deviation of the sample measurements was 4 μg/m3, you are 99.7% confident that actual concentration of fine particulates at the school is . a=21.3μg/m3 -22.7μg/m3 b=21μg/m3- 23μg/m3 c=18μg/m3-26μg/m3 d=21.7μg/m3-22.3μg/m3