Which expression is equivalent to StartFraction negative 18 a Superscript negative 2 Baseline b Superscript 5 Baseline Over Negative 12 a Superscript negative 4 Baseline b Superscript negative 6 Baseline EndFraction? Assume a not-equals 0, b not-equals 0. StartFraction 2 a squared b Superscript 11 Baseline Over 3 EndFraction StartFraction 2 a squared b Superscript 30 Baseline Over 3 EndFraction StartFraction 3 a squared b Superscript 11 Baseline Over 2 EndFraction StartFraction 3 a squared b Superscript 30 Baseline Over 2 EndFraction