问题
单项选择题
The owner of a firm gathers some information about her business. This year the firm's revenue is $300000. Cash expenses are $170000. Normal profit is $70000. Economic depreciation is $20000. If the owner could have earned $30000 per year in wages working for another company, the firm's economic profit is closest to:（）
A. $10000
B. $30000
C. $60000
答案
参考答案：A
解析：
经济利润(economic profit)等于总收入减去显性成本和隐性成本，现金费用是显性成本，正常利润、经济折旧和放弃的收入等属于隐性成本。300000-170000-70000-20000-30000=10000(美元)。
=3.20cm，
=4.52cm，
=8.42cm，
=9.70cm，则木块的加速度大小
= m/s2（保留两位有效数字）。
= （重力加速度为g，木块的加速度为