The highest mass peaks in the mass spectrum of Br₂ occur at m/Z 158, 160, and 162. The ratio of intensities of these peaks is approximately 1:2:1. Bromine has two stable isotopes, ⁷⁹Br (50.7% abundance) and ⁸¹Br (49.3% abundance). 

(a). What molecular species gives rise to each of these peaks? 

(b). Explain the relative intensities of these peaks.