Please help - calculate weekly averages (many criteria)

Hello,

Would someone kindly help with a formula to calculate weekly averages based on Product (and features, platform, wheelbase) please?

Someone already helped me with a formula for monthly averages - can someone help modify the formula to calculate weekly averages please?

=SUM(IF(FREQUENCY(IF((ROUNDUP(MONTH($A$2:$A$100)/3,0)=MID(AG$4,2,1)+0)*(YEAR($A$2:$A$100)=VALUE(RIGHT(AG$4,4)))*($C$2:$C$100=AG$5),MONTH($A$2:$A$100)),{1,2,3,4,5,6,7,8,9 ,10,11,12}),1))


Weekly data file:

https://dl.dropboxusercontent.com/u/...20average.xlsx


Attached below as well:

Excel Question - quarterly average.xlsx


Thanks!