Which term refers to the cost that motivates an economic decision

Which term refers to the cost that motivates an economic decision? Incentive.  An incentive is something that motivates or encourages someone to do something. In this case, when the cost of a good or service motivates the economy to make a decision, the cost is the incentive that is driving the person to do something. The investment is usually greater or the output becomes greater depending on the cost that is driving it.

answer: marginal utility of the fourth brownie is 0.

explanation: marginal utility is the addtional utility gained from the consumption of one more unit of a good. it is given by,

so, marginal utility at the 4th unit will be given by

since, the values are not given here, you can simply find marginal utility at fourth unit by subtracting total utility at 3rd unit from total utility at 4th unit.