Level 5:1.25× (1-0.1) =1.125.

Grade 6:1.125× (1+0.1) =1.2375.

Grade 6 -3 = 38 Grade 3: 38 ÷ (1.2375-1) =160 (person)

Level 4: 160× 1.25=200 people.

Grade 5: 200× (1-0.1) =180 (person)

Grade 6:180× (1+0.1) =198 (person)

Grade three+grade four+grade five+grade six =160+200+180+198 = 738 (person)