A tractor-trailer loses 8 psi during the stabilized full service-brake leak test. Why is this a problem under Alberta's guide?

1. For one trailer, the guide's formula allows 4 psi for the power unit plus 2 psi per trailer, so 8 psi exceeds the limit
2. Any pressure loss above 20 psi is acceptable
3. The leak test is optional after a tug test
4. Air loss never matters if the truck starts