Find the error intervals for the following rounded numbers

Question 1:

20000 (1 s.f.)

15000≤x<25000

Question 2:

2.11 (2 d.p.)

2.105≤x<2.115

Question 3:

3.5 (2 s.f.)

3.45≤x<3.55

Question 4:

90000 (1 s.f.)

85000≤x<95000