Counting active projects and available tasks

I’m totally new to AppleScript. Looking at examples found in the forums I was able to come up with the following script to count available tasks.

tell application "OmniFocus"
	set theDoc to default document
	tell theDoc
		set allAvailableTasks to count (every available task of every flattened context)
		display dialog "Number of available tasks: " & allAvailableTasks
	end tell
end tell

How do I add the count of active projects?