Could or would: I see. Would/Could you ask her to call me?

[Mdenglish]

Hi everyone :D ,

Which expression is better to use in the following phone conversation?

A: Hello, John. Kate is out.

B1:I see. Could you ask her to call me ?
or
B2:I see. Would you ask her to call me ?

Thanks in advance,

mdenglish

[Arindam]

Better to use 'could' as it is more polite.