Good old useless passenger side mirror!

My Duster has a factory passenger side mirror and it is further back on the car than the driver's side one. If someone is on your rear 1/4 panel to your right or behind that, you can see them in the mirror. Seems like it works okay to me...

How much further back is the passenger mirror than the driver's ? I have one to install on my 75 duster. Thanks.