og 13 56题。。。求大家帮忙解答

萧章may

求详解 谢谢～
我明白2:3:5:6
所以
if 2x＝30，x＝15
if 3x＝30，x＝10
if 5x＝30， x＝6
if 6x＝30， x＝5

为什么要2x+3x+5x+6x＝16x？谢谢大神 后面的就不太明白了

56.Four staff members at a certain company worked on a project.  The amounts of time that the four staff members worked on the project were in the ratio 2 to 3 to 5 to 6.  If one of the four staff members worked on the project for 30 hours, which of the following CANNOT be the total number of hours that the four staff members worked on the project?

A.     80

B.       96

C.     160

D.     192

E.       240