[AccessD] calculation

Hello Group,

i need to calculate the percentage(%) of the value B3 in access for the total of numbers of B.

The table that is have:

ID    patient    B
1     AA         1
2     AA         1
3     AA         2
4     AA         3
5     BB         1


Query:

patient    B(%)
AA         25

How can i do this?

Thanks

Pedro