please help just in steps number 6 & 9, write the code with SQL statment , especially 6

For analysis purposes, Decision-Makers want to classify the Customers according to the Turnover of each one according to the following: The Turnover of a customer is the total amount of all his Orders. This data is not in the DB tables; therefore, you need to calculate it in order to determine the Customer Type. The Type of a customer depends on his Turnover. We expect three types of customers noted 'A', 'B' and 'C. The Type is: o 'A' if the Turnover Avg_Turnover (where Avg_Turnover is the Average Turnover of all customers). O'B' if 0.5 * Avg_Turnover