Studies show that the concentration of PCBs is much higher in malignant breast tissue than in normal

Question:

Studies show that the concentration of PCBs is much higher in malignant breast tissue than in normal breast tissue. If a study of 50 women with breast cancer reveals an average PCB concentration of 22.8 x 10-4 gram, with a standard deviation of 4.8 x 10-4 gram, is the mean concentration of PCBs less than 24 x 10-4 gram?