Question 4 (10 Points] Consider the following relational schema for an online programming platform: Users User ID Username Password Rank Questions Question ID Question title difficulty level description date posted Submissions User ID Question ID solution status points date Write appropriate SQL queries for the questions below. For each question write a single query: A. Retrieve the username and ranks of all users from highest to lowest rank [3] B. Retrieve the username, id and rank of all users who have the lowest rank [3] C. Retrieve the total number of submissions for each question with "medium" difficulty level. The query should show question id and number of submissions [4]