Maximum & Minimum Dates based on Condition

Hi,

I'm trying to get the maximum and minimum dates in a range based on an Identity, and then sum a quantity (of widgets) based on the dates in that range.

I can do this individually, but want to be able to sum on the whole range...

In the atached spreadsheet, for Identity 1, the total widgets is 420, completed in 488 days.

For identity 2, the total widgets is 1242, completed in 488 days.

My problem is working out the number of days in the range based on the Identity number.

I'm having difficulty determining how to get the max date based on Identity 1... i've tried SUMPRODUCT(MAX(Date Range))*(Identity Range = 1))

I also need to get the minimum date for the same identity, which I assume will similar.

I'd appreciate any pointers. Tks.