At the beginning of summer, the water level on a pond is 2 feet below its normal level. After an unusually dry summer, the water level on the pond dropped another 2 feet. How far above or below the normal water level is the pond at the end of the summer?

Consider u = {x|x is a negative real number}which is an empty set? o {x|x eu and x has a negative cube root}o {x|x eu and x has a negative square root}{x|x eu and x is equal to the product of a positive number and -1}{x|x eu and x is equal to the sum of one negative and one positive number?