Kamala and Donald work for the same retail clothing company. Kamala started working with the company as a manager of the children's department. She has a business degree, five years of experience in retail sales, and has excellent customer relationship skills. She is paid $60,000 per year plus benefits. Donald also has a college degree but his degree is in communications. He has six years of experience as a retail sales manager in the men's department of a clothing company, and spent a year on the staff of a famous clothing designer where he gained unique insights into how clothing is made, how fabrics are selected, and the different properties of different fabrics. He is paid $80,000 per year plus benefits. Kamala and Donald were discussing their compensation during lunch one day and Kamala was quite upset to learn that Donald was paid so much more than she was being paid. What is the issue that has caused Kamala to be upset