There will always be some controversy over this issue of Vmp being best ROC speed for a prop as it depends on which text book you read and the interpretation of the position of the power available line which depends on propeller efficiency.

In our diagram on 5.8 we suggest that it is somewhere between Vmp and Vmd.

As far as the exam is concerned we must stick with the examiners interpretation which is that Vmp gives best ROC speed for the prop.

Prop holding speed is Vmp giving maximum endurance which in this question is 95kts