Task: Text to Code
Input (English): Step 1: For each row in classroom table, find the corresponding rows in time_slot table.
Step 2: find the number of rows in the results of step 1 whose end_hr greater than 50 and building equals Alumni
Output (English): SELECT Count ( * ) FROM classroom AS T1 JOIN time_slot AS T2 WHERE T2.end_hr > 50 AND T1.building = "Alumni"