CREATE TABLE table_name_87 (field_goals INTEGER, touchdowns VARCHAR(255), player VARCHAR(255), points VARCHAR(255), extra_points VARCHAR(255))
When Herb Graver played, how many field goals were made when there were more than 50 points, less than 15 touchdowns, and more than 0 extra points?
    
SQL: SELECT AVG(field_goals) FROM table_name_87 WHERE points > 50 AND extra_points > 0 AND player = "herb graver" AND touchdowns < 15