Mark Hirschey的managerial economy 书里有一习题，看答案涉及到用Marginal Analysis，这也很好理解，但问题B的答案说要使用largest marginal sales 来分配各地区营业天数，查了半天资料也没见详细的解释，求知道的大牛赐教如何确定。


附题，Marginal Analysis: Tables. Sarah Berra is a regional sales representative for Dental Laboratories, Inc. Berra sells alloy products created from gold, silver, platinum, and other precious metals to several dental laboratories in Maine, New Hampshire, and Vermont. Berra's goal is to maximize her total monthly commission income, which is figured at 10% of gross sales. In reviewing her monthly experience over the past year, Berra found the following relations between days spent in each state and monthly sales generated:

	Maine	New  Hampshire	Vermont
Days	Gross Sales	Gross Sales	Gross Sales
0	$4,000	0	$2,500
1	$10,000	$3,500	$5,000
2	$15,000	$6,500	$7,000
3	$19,000	$ 9,000	$ 8,500
4	$22,000	$10,500	$ 9,500
5	$24,000	$11,500	$10,000
6	$25,000	$12,000	$10,000
7	$25,000	$ 12,500	$10,000

A. Construct a table showing Berra's marginal sales per day in each state.
B. If administrative duties limit Berra to only 10 selling days per month, how should she spend them?
C. Calculate Berra's maximum monthly commission income.