A high-resolution mass spectrum of element R displays four isotopes with the data below.
Isotope Mass (amu) Peak area
85R 84.911 47
87R 86.909 265
88R 87.907 19
89R 88.905 3
Determine the average atomic mass of element R, expressed in g·mol−1, to the nearest 0.001.
a) 86.909g⋅mol−1
b) 87.158g⋅mol−1
c) 86.703g⋅mol−1
d) 86.794g⋅mol−1