Marginal utility can be rev: 04_09_2018 multiple choice positive, but not negative. positive or negative, but not equal to zero. positive, negative, or equal to zero. decreasing, but not negative.

  positive, negative, or equal to zero

Step-by-step explanation:

Marginal utility is the derivative of the utility function. That function may be increasing or decreasing and may have a turning point. Hence the marginal utility can have either sign or be zero.

b

step-by-step explanation:

the solution is 12x-6y