A spring of stiffness $k$ supports a box of mass $M$ in which is placed a block of mass $m$. If the spring is pulled downward a distance $d$ from the equilibrium position and then released, find the force of reaction between the block and the bottom of the box as a function of time. For what value of $d$ does the block just begin to leave the bottom of the box at the top of the vertical oscillations

the answer would be voluntary exchange -

"the act of buyers and sellers freely and willingly engaging in market transactions. moreover, transactions are made in such a way that both the buyer and the seller are better off after the exchange than before it occurred."

hope this : )

-shy

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.