20 or 28, both are ideal.
As an aside, I just had about 20 Gambel's walk through my yard picking tidbits out of my stones (I have Arizona landscaping). I no longer hunt but they are fun to watch.
"Guard with jealous attention the public liberty. Suspect everyone who approaches that jewel. Unfortunately, nothing will preserve it but downright force. Whenever you give up that force, you are inevitably ruined.”
Patrick Henry
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