Calculates the value of the mark

Question

Create table LAB7_GRADES with 5 columns: ID Number student id T1 Number mark from test 1 T2 Number mark from test 2 T3 Number mark from test 3 MARK Number average mark from test 1, 2 and 3. Create a trigger LAB7_GRADES_TRG that calculates the value of the MARK column.