> If the constraint is 4 hours, the manager can't expect nothing but 4h quality.
Yes, but how does the manager estimate that it indeed typically should take 4 hours when the numbers he gets are:
1. From his employees who work at that company, intimately familiar with the problem domain, tools and possibly came up with the problem statement in the first place and solved it in 4 hours after thinking about and working on it with no other distractions
2. From candidates self reporting the time it took to complete the problem severely undereporting the time it took them because they want to impress the employer?
Is 4 hours of focused, uninterrrupted time equal to 8 4 hours of unfocused, interrrupted time?
If the constraint is 4 hours, the manager can't expect nothing but 4h quality.