问题如下图：老师这个4.5的意思是每个产品的MR是4.5对吧
选项：
A. 
B. 
C. 
解释：
老师 以下两种题型的对比，解题方式都不同。能够详细一下吗？谢谢！ 1，An is a businessmselling socks in the locmarket. If 100 pairs of socks are sol he cearn a totrevenue of $500. If 120 pairs of socks are sol the totrevenue will $590. The marginrevenue of socks with a market 120 pairs of socks is: 2，Emma sells homema cakes in New York. Everyy she csell 250 cakes with a priof $10. She offers speciscount on Mother's y anexpecteto sell 350 cakes with a scountepriof $8. The marginrevenue per cake she sells from speciscount is:
with a market 120 pairs of socks 怎么理解
