Weight
w
(kg) Frequency
0 ≤
w
< 20
a
20 ≤
w
< 30
b
30 ≤
w
< 40
c
40 ≤
w
< 60
d
60 ≤
w
< 80
e

a
=

b
=

c
=

d
=

e
=