Geoffrey is evaluating the expression StartFraction (negative 3) cubed (2 Superscript 6 Baseline) Over (Negative 3) Superscript 5 Baseline (2 squared) EndFraction as shown below. StartFraction (negative 3) cubed (2 Superscript 6 Baseline) Over (Negative 3) Superscript 5 Baseline (2 squared) EndFraction = StartFraction (2) Superscript a Baseline Over (negative 3) Superscript b Baseline EndFraction = StartFraction c Over d EndFraction What are the values of a, b, c, and d? a = 4, b = 2, c = 16, d = 9 a = 4, b = negative 2, c = 16, d = 9 a = 8, b = 8, c = 256, d = 6,561 a = 8, b = 8, c = 256, d = negative 6,561