Final answer:
The length of the coat left by a #4 blade isn't relevant to the physics concept being described, which is the moment of inertia for a set of rotating blades, multiplied by four to account for each blade.
Step-by-step explanation:
The question appears to be concerned with the moment of inertia of a blade as part of a physics problem, rather than the length of a coat on a grooming blade. Nonetheless, in the context provided, it is explained that the moment of inertia of one blade, which can be likened to a thin rod rotated about its end, will be multiplied by four to account for all the blades. Therefore, the total moment of inertia (I) is the moment of inertia for one blade times four.