单项选择题
A.S=0.8×0.993D+0.2; B.S=0.8×0.993D+0.1; C.S=0.866×0.993D+0.2; D.S=0.866×0.993D
A.13、5; B.13.5、5,5; C.14、6; D.14.5、6
A.50; B.80; C.100; D.30