PLEASE HELP WITH THIS PRACTICE PROBLEM FROM MY MANANGERIAL ACCOUNTING CLASS:

Consider a company that sells prescription drugs. It has salespeople who visit doctors and hospitals to encourage physicians to prescribe its drugs. The company sells to drugstores. Salespeople are paid a salary plus a bonus if actual sales exceed planned sales. To plan operations, this company needs to develop estimates of total sales. Where should it get this information?

PLEASE BE DETAILED AS I AM PRETTY CONFUSED ABOUT THIS PROBLEM. THANK YOU.