250 days extra. This is an indirect variation. So, k = m × d = 300 × 20 = 6000. After 100 days m = 20 - 4 = 16. So therefore, k = 200 × 20 = 4000. Since there were 16 workers now, since 4 left, so now 4000/16 = 250.
Hope it helps you!
Bye!
