两道数学真题请教

1，A certain quantity is measured on two different scales, the R-scale and the S-scale, that are related linearly. Measurements on the R-scale of 6 and 24 corrsepond to measurements on the S-scale of 30 and 60 respectively.What measurement on the R-scale corresponds to a measurement of 100 on the S-scales?

A,20.B,36.C,48.D,60.E,84

答案是C，一点都不明白这题怎么算的。

2，For each landscaping job that takes more than 4 hours, a certain contractor charges a total of r dollars for the first 4 fours plus 0.2r dollars for each additional hour or fraction of an hour, where r>100. Did a particular landscaping job take more than 10 hours?

(1) the contractor charge a total of $288 for the job.

(2) the contracdtor charge a total of 2.4r dollars for the job.

答案是b，但是我觉得（1）￥288<4*100(根据条件r>100)，所以工作时间一定小于10小时，能够回答问题，为什么不选（1）和（2），也就是d答案呢？

1 S=kR+d

2 a total of r dollars for the first 4 fours ==> be careful when reading