"the" and "a"

[njanja]

Which article is more appropriate in these sentences?

I like the American accent.
I like an American accent.
I told them i would take a number 84 bus.
I told them i would take the number 84 bus.
..........................take bus number 84
..........................take the bus number 84
..........................take a bus number 84


She walked into a boutique and asked how much the dress was.
She walked into a boutique and asked how much a dress was.

They were sitting in a restaurant and a waiter....
They were sitting in a restaruant and the waiter...

[Tdol]

1 The normal one would be 'the American accent', but as there are many, 'a' could be used.
2 You could use both for the bus, though 'the 84' would be more common.
3 Most likely 'the'- a specific dress.
4 Most likely 'the waiter' as mentioning the restauran makes it specific, but if there are many waiters 'a' could be used.