Just one, but first the tire really has to want to change.
He wanted to be published on Pork Avenue.
You use a cow-culator. Or you round them up. Or any other method the commenters want.
Just one but he has to coordinate ten other professionals who are doing this quiet complicated task.
None that's a hardware problem
Just one, but the light bulb is going to need to change itself.
On a Freudian Slip
A tire.