Task: Text to Code
Input (English): Find the average grade point of student whose last name is Smith.
Output (English): SELECT avg(T2.gradepoint) FROM ENROLLED_IN AS T1 JOIN GRADECONVERSION AS T2 JOIN STUDENT AS T3 ON T1.Grade  =  T2.lettergrade AND T1.StuID  =  T3.StuID WHERE T3.LName  =  "Smith"