问题如下：
Exhibit 1 Grey Family: Personal and Financial Information:
Personal Information:
1. Estimated present value of the Greys’ future earnings is $3,900,000.
2. The family has two children, ages 10 and 8. Cost of four years of university for the two children, with an estimated present value of $250,000.
3. Purchase of a vacation home in the next five years, with an estimated present value of $325,000.
4. Estimated present value of the Grahams’ future consumption is $3,500,000.
Financial Information:
Using the data in Exhibit 1, the Greys’ economic net worth (in thousands) is closest to:
选项：
A.$755
B.$679
C.$854
解释：
B is correct.
考点：economic balance sheet
解析：economic balance sheet不仅包含了传统的资产和负债，还包含了extended assets & liabilities，例如养老金、未来消费的现值。所以计算过程中既要包含表格中的财务信息，也要包含表格上方的4条个人信息。其中，
Total economic assets = PV of future earnings+ Checking account+ Taxable investment account+ Residence=3900+27+625+525=$5077 (in thousands)
Total economic liabilities= PV of education + vacation home+ PV of future consumption+ Residential mortgage+ Outstanding balance on line of credit=250+325+3500+285+38=$4398 (in thousands)
所以Economic net worth=5077-4398=679 (in thousands)
outstanding balance line of credit是什么意思，请问为什么要这样处理，谢谢
