Using Indefinite Articles 3

Which indefinite article should we write in front of the following words -'a' or 'an'?

1. __________ number

a
an

2. __________ heater

a
an

3. __________ interview

a
an

4. __________ application form

a
an

5. __________ heir

a
an

6.__________ computer

a
an

7.__________ bag

a
an

8. __________ octopus

a
an

9. __________ ewe

a
an

10. __________ fridge

a
an