焊后热处理的方式有几种？
参考答案：
后热、高温回火、正火加回火处理。
用铆钉将钢结构的零件和部件连接在一起的称为（）。
An investment with a cost of $ 5000 is expected to have cash inflows of $ 3000 in year 1, and $4000 in year 2. The internal rate of return (IRR) for this investment is closest to.（）
A. 15%.
B. 30%.
C. 25%.
