The following bar graph shows the production of pens (in lakhs) by three companies M, N, O from 2018 to 2022. What is the ratio of the average production of Company O in the period 2019-2021 to the average production of Company M in the same period ?

64 : 73

Average production of O in 2019 - 2021  :  Average production of M in 2019 - 2021

\(\frac{15 + 18 + 31 }{3}\)  : \(\frac{21 + 33 + 19 }{3}\) 

  64  :  73