What is the percentage of "surface" object samples in image No.2654?
DIVIDE(SUM(OBJ_CLASS_ID where OBJ_CLASS = 'surface'), COUNT(OBJ_CLASS_ID)) as percentage where IMG_ID = 2654;
SELECT CAST(SUM(CASE WHEN T2.OBJ_CLASS = 'surface' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T1.OBJ_CLASS_ID) FROM IMG_OBJ AS T1 INNER JOIN OBJ_CLASSES AS T2 ON T1.OBJ_CLASS_ID = T2.OBJ_CLASS_ID WHERE T1.IMG_ID = 2654