Nested Countif Question

Can someone help me formulate the correct syntax for a nested countif question?

I have a report where I need totals from multiple columns that match certain criteria.

Question Background:

Column D asks a simple yes/no question of if a the line item equipment has been completed or not.
“Has the equipment been upgraded?” – Yes/No

Column L indicates which of the two locations the equipment is from. California and Arizona are the two locations.
“What location is the unit in?” CA or AR

There are 206 units in Arizona and 460 in California

So basically I need a countif that will first count the number of units from column L that match California, but that also have a matching criteria of “Yes” in Column D

Any suggestions?