Cindy and her husband, Trevor, own a small pool shop in Noordwyk that sells pool chemicals and provides pool maintenance services. Cindy is responsible for ensuring that enough stock is available to sell and for Trevor to use for cleaning and servicing customers’ pools. In most instances, they need a bigger supply of chemicals to satisfy customer demand. Trevor does not keep his appointments to service pools due to a lack of the required chemicals. Which of the following skills would you advise Cindy to acquire to manage the business well?