tolong dijawab ya yang bisa.....

L diarsir = L acb - L aeb + L adb - L aeb
L diarsir = L acb + L adb - 2.L aeb
L diarsir = (ab × t /2) + (ab × t /2) - 2(ab × t /2)
= (20 × 32 /2) + (20 × 28 /2) - (20 × 10)
= (20 × 16) + (20 × 14) - (200)
= 320 + 280 - 200
= 400