Arnold is the chief executive officer of Beta Corporation. Arnold's responsibilities include decisions on product development, marketing, and other significant business directions. Arnold is subject to the approval and oversight of Beta's board of directors. Carol is a Beta manager whose duties include the firm's day-to-day hiring, firing, purchasing, and selling. Dave is a Beta salesperson, whose daily activities are controlled by Carol. Erin writes technical manuals for Beta products according to Arnold's instructions and subject to Beta's control, but has no dealings with Beta customers or suppliers. Fred edits the manuals on a contract-per-manual basis and is not otherwise subject to Beta's control. Who is a principal? Who is an agent? Who is an employee? Who is an independent contractor? Explain.