Find the error intervals for the following rounded numbers

Question 1:

0.0091 (2 s.f.)

0.00905≤x<0.00915

Question 2:

3.8 (1 d.p.)

3.75≤x<3.85

Question 3:

20 (1 s.f.)

15≤x<25

Question 4:

850 (2 s.f.)

845≤x<855