A cross-section of an irrigation canal is a parabola. If the surface of the water is 40 feet wide and the canal is 16 feet deep at the center, how far down (from the surface) is the level where it is 20 feet wide?

Abag contains 4 red, 7 blue and 5 yellow marbles. event a is defined as drawing a yellow marble on the first draw and event b is defined as drawing a blue marble on the second draw. if two marbles are drawn from the bag, one after the other and not replaced, what is p(b|a) expressed in simplest form? a. 7/16 b. 7/15 c. 14/16 d. 14/15