Let's define someone at risk for sustaining a bone fracture as someone having a bone mineral density (BMD) below the 95^th percentile of the age, race, and sex distribution scale. The average total body BMD for a white woman who is 55 years living in the US is 876139 mgcm^-2. Mrs. Q has a BMD of 856 mgcm^-2.

a. Calculate a Z-score for Mrs. Q's BMD

b. Is Mrs. Q at risk for a bone fracture?? Why or why not?