Final answer:
The question lacks context, but in mountaineering literature, climbers are commonly advised to spend no more than 15 to 30 minutes on a summit for safety reasons.
Step-by-step explanation:
The information provided suggests that Russell is giving advice to Terry, but without additional context, it is unclear what specific advice regarding time on the summit is given. In literature dealing with mountaineering, it is commonly recommended to minimize time spent on a summit due to the potential dangers of altitude sickness and changing weather conditions.
Typically, climbers are advised to spend no more than 15 to 30 minutes on a summit, especially at high altitudes, to reduce health risks and ensure enough time for a safe descent before conditions deteriorate.
Russell advises Terry to spend no more than around fifty feet on the summit. This is because, as indicated in the provided information, the summit is made of solid diamond, except for the top layer of sod and gravel. Spending more time on the summit could be dangerous or lead to damage to the valuable diamond mountain.