When there is a Crescent Moon in the night sky, how much of the entire Moon’s surface is actually lit by the Sun? Why? Please help me!!! And answer the why part, I already know that 50% of the Moons surface is actually lit by the Sun.

Water is siphoned from a large tank and discharges into the atmosphere through a 50-mm diameter tube. the end of the tube is b = 2.6 m below the tank bottom which is a = 6.7 m deep, and viscous effects are negligible. determine the maximum height h over which the water can be siphoned without cavitation occurring. atmospheric pressure is 101.4 kpa, and the water vapor pressure is 1.79 kpa (absolute). report your answer in meters to two decimal places.