已知X服从参数为1的指数分布，Y=|X|，试求：
参考答案：F(x，y)=P{X≤x，Y≤y}=P{X≤x，|X|≤y}=P{X≤x，X≤y
We had a big meal in a fine restaurant last Monday and the total cost ____________ $500.
A．came through
B．came in
C．came out with
D．came to
锅炉稳定运行时，给水调节机构允许（）。
