I need help with this question: Booth Financial Services LLC has two revenu

I need help with this question:

Booth Financial Services LLC has two revenue producing departments Financial Planning and Business consulting. The accounting department is trying to
determine the bes method to allocate $1000000 of common cost (Secretarial staff reception personel etc) either by salary or number of employees.
Information on the revenue department are as follows:

Depatment Employees Salaries

Financial planning 150 employee 10000000

Business consulting 50 employees 5000000

A. Allocate the 1000000 common cost to the two revenue departments using both methods

B. Why are the allocations called arbitary