Based on the information given below, divide the companies into three groups according to the average annual cost of fixed production assets and calculate:

a$)$ the total length of service of employees in each group;

b$)$ the total average annual value of the main production funds per group;

c$)$ volume of manufactured products per group;

d$)$ the total average annual value of the main production funds and the volume of the manufactured product per company for each group.

$($Organization of statistical grouping and problem solving related to graphic representation.$)$