If the Federal Reserve buys $8,500 worth of securities from non-bank public, and the non-bank public then keeps the payment from the bank as cash, then a: R increases by $8,500 and the MB rises by $8,500
b: C and R both increase by $8,500, and the MB does not change
c: C increases by $8,500 and the MB increases by $8,500
d: C increases by $8,500 and the MB does not change

c: C increases by $8,500 and the MB increases by $8,500

Explanation:

If the Federal Reserve buys $8,500 in securities from non-bank public and then payment is kept from the bank in form of cash, theC increases by $8,500 and the MB increases by $8,500

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.