average duration for canceled bills

[kghisla]

Hi, I need a formula calculating the average just for canceled bills.

i have #3 columns:
#1 to identify the client
#2 p=pending c= canceled
#3 #of days on pending until bill is canceled.

I need to know the average # of days of canceled bills per each client.

please see dummy file attached.

thank you very much for your help.

carlo