本人微观菜鸟一枚，现在复习考试，水平太差，有很多题不会，希望得到各位大牛指点，在此给各位鞠躬了、
Bob and Ray are thinking of buying a sofa. Bob's utility function is UB(S, MB) = (1 + S)MB and Ray's utility function
is UR(S, MR) = (3 + S)MR where S = 0 if they don't get the sofa and S = 1 if they do and where MB and MR are the
amounts of money they have respectively to spend on their private consumptions. Bob has a total of $800 to spend
on the sofa and other stuff. Ray has a total of $1,600 to spend on the sofa and other stuff. The maximum amount that
they could pay for the sofa and still arrange to both be better off than without it is
A. $533.33.
B. $1,200.
C. $1,600.
D. $800.
E. $450.
大家棒棒忙，看看怎么做，最好有几步过程，我的底子不太好，谢谢