Thandi is the Senior Service Adviser at a premier vehicle dealership. She and her team act as the interface between customers who want their cars serviced and repaired and the 16 technicians who carry out the work in their state-of-the-art workshop. 'There are three types of work that we have to organise,' says Thandi. 'The first is performing repairs on customers' vehicles. They usually want this done as soon as possible. The second type of job is routine servicing. It is usually not urgent,The remainder of our work involves working on the pre-owned cars, which our buyer has bought to sell to customers. Most days, we deal with 50 to 80 jobs, each taking from half an hour to a whole day,' Thandi estimates. 'To enter a job into our process, all service advisers have access to the computer-based scheduling system. 'We keep all the most commonly used parts in stock,' Thandi continues, 'but if a repair needs a part that is not in stock, we can usually get it from the manufacturer's parts distributors within a day. 'We keep all the most commonly used parts in stock,' Thandi continues, 'but if a repair needs a part that is not in stock, we can usually get it from the manufacturer's parts distributors within a day. We can cope with most of these uncertainties because our technicians are flexible in terms of the skills they have and also are willing to work overtime when needed. Also, it is important to manage customers' expectations. 

Identify and critically discuss the four vital activities of the planning and control system that Thandi manages.