When a frog point is broken out more than 5/8 inches down and 6 inches back, what is the maximum speed allowed over that frog?

The correct answer is based on the guidelines for maintaining safety standards when dealing with trackwork irregularities, such as a frog point. A frog point is a part of a switch where the two rails converge and forms a point. When the frog is broken out more than 5/8 inches down and 6 inches back, it indicates a significant deviation from the normal track profile, which can lead to potentially unsafe conditions for train operations.

In situations like these, a maximum speed of 10 MPH is allowed as it significantly reduces the risk of derailments or other accidents that could occur if a train were to traverse this irregularity at higher speeds. This speed restriction is established to ensure that trains can safely navigate the area while maintaining enough stability as they pass over the frog.

Higher speeds like those indicated in the other options could compromise the safe handling of the train, especially considering the structural integrity of the track may be compromised. Therefore, the 10 MPH limit is a precautionary measure that prioritizes safety in respect to the degree of deviation in the track at the frog point.