Himanshu is working as 'a 'Marketing Manager' in 'Suvidit-Air-Conditioners', a well known brand in the field of air-conditioners. Till last month the company was able to achieve its sales targets. But this month Himanshu observed that targets were not being met and the number of air-conditioners sold was decreasing. He analysed the situation and found that the new salesman appointed last month was not good and for this he took necessary action.
Which of the following functions of management helped Himanshu to identify the decrease in sale?