Therefore forecasting the manpower needs of Ya Kun, I would use trend analysis. This is the study of a firm past employment needs over a period of years to predict their future needs. As for Ya Kun, they have many years of operating experience, therefore they can predict their manpower needs easily according to past records. For example, assuming that they have been sticking to the traditional employment pattern of approximately 12 staffs working each at two shifts per outlet. This employment pattern seem to be most efficient for Ya Kun, therefore Ya Kun should stick to this number of employees.
However, other factors (like changes in the sales volume and productivity) also affects staffing needs, therefore if Ya Kun would like to increase the other factors, they would need to refer to other analysis such as ratio analysis or scatter plot.