Marina correctly simplified the expression the fraction with numerator negative 4 A to the negative 2 power b to the 4th power and denominator 8 A to the negative 6 power b to the negative 3 power , assuming that A is not equal to 0 and b is not equal to 0 Her simplified expression is: negative 1 half A to the 4th power b to the square th power What exponent should Marina use for b ?