Which shows the following expression after the negative exponents have been eliminated? startfraction a cubed b superscript negative 2 baseline over a b superscript negative 4 baseline endfraction, a not-equals 0, b not-equals 0 startfraction a cubed b superscript negative 4 baseline over a b superscript negative 2 baseline endfraction startfraction a b superscript 4 baseline over a cubed b squared endfraction negative startfraction a cubed b superscript 4 baseline over a b squared endfraction startfraction a cubed b superscript 4 baseline a b squared endfraction.