1. 计算1^2+2^2+......+10^2

2. 一个期限为两年的项目，初始投资为2000美元，预期在第1年年末产生800美元收益，第2年年末产生1600收益投资，计算该项目的内部收益率IRR

3. 某人贷款20000元购买汽车，年利率为6%，他需要在5年内进行每月的分期付款，问他每个月需要支付多少钱(. calculate 1^2+2^2+... +10^2　　　 2. a two-year project with an initial investment of $2000 is expected to generate $800 in revenue at the end of first, generating a 1600 return on investment at the end of second. The internal rate of return for the project is IRR　　　3., someone loans 20000 yuan to buy a car, the annual interest rate is 6%, he needs 5 months in the monthly installment, ask him every month how much to pay)