Apple's stock has generated the following annual returns over the past 5 years: 2016: 10.0%, 2017: 46%, 2018: -6.8%, 2019: 86%, 2020: 81%. What was the realized average annual return over this period?

a) 138% b) 46% c) 43% d) 38% (right answer but how do i calculate this?) e) 216%