The agent shall appoint such deputy agents and other assistants as may be necessary to direct the marketing program. Such appointments are subject to the approval of the program committee. The agents, deputy agents, and other assistants are employees of the proration zone and not of the state. An officer or employee shall not receive compensation which is based on a percentage of volume which is involved in a marketing program, or in any manner that would lend encouragement to the promotion of a marketing program for the purpose of increasing salaries and income.