Write a select statement that answers this question: what is the total quantity purchased for each product within each category? return these columns: category_name the category_name column from the category table name_of_product the product_name column from the products table quantity_purchased the total quantity purchased for each product with orders in the order_items table use the with rollup operator to include rows that give a summary for each category name as well as a row that gives the grand total. use the if and grouping functions to replace null values in the category_name and product_name columns with literal values if they’re for summary rows.