ANS:C - both (a) & (b).

Let's break down the concepts of range and approach in the context of a cooling tower and explain how they are calculated:

1. Range:
   • The range refers to the temperature difference between the hot water inlet temperature and the cooled water temperature (exit water temperature) in a cooling tower.
   • It represents the extent of cooling achieved by the cooling tower as the hot water passes through it.
   • In this case, the hot water enters the cooling tower at 95°F and exits at 80°F. Therefore, the range is calculated as: Range = Hot water inlet temperature - Exit water temperature = 95°F - 80°F = 15°F
   • So, the range in this case is 15°F, indicating that the cooling tower reduces the temperature of the hot water by 15°F as it passes through.
2. Approach:
   • The approach refers to the temperature difference between the cooled water temperature (exit water temperature) and the wet bulb temperature of the air entering the cooling tower.
   • It represents how closely the cooled water temperature approaches the lowest temperature that can be achieved by evaporative cooling, which is the wet bulb temperature of the air.
   • In this case, the wet bulb temperature of the air entering the cooling tower is 70°F, and the cooled water exits at 80°F. Therefore, the approach is calculated as: Approach = Exit water temperature - Wet bulb temperature = 80°F - 70°F = 10°F
   • So, the approach in this case is 10°F, indicating that the cooled water temperature is 10°F higher than the wet bulb temperature of the air entering the cooling tower.

In summary, the range represents the temperature reduction achieved by the cooling tower, while the approach indicates how closely the exit water temperature approaches the wet bulb temperature of the air. In this case, the range is 15°F, and the approach is 10°F.