What is the following sum? Assume x greater-than-or-equal-to 0 and y greater-than-or-equal-to 0 StartRoot x squared y cubed EndRoot + 2 StartRoot x cubed y Superscript 4 Baseline EndRoot + x y StartRoot y EndRoot x squared y squared StartRoot y EndRoot minus 2 x y squared StartRoot x EndRoot 2 x y StartRoot y EndRoot + 2 x y squared StartRoot x EndRoot 4 x y StartRoot x Superscript 5 Baseline y Superscript 8 Baseline EndRoot 2 x y StartRoot x y EndRoot