这题应该怎么做？ 我一点方向也没有！

23. A component fails on the average of once every 4 years with 75% of the failures observed to occur during stormy weather. If there are 12 hours of stormy weather to every 240 hours of good weather, what are the failure rates for stormy and good weather, respectively?

a) λ (stormy)=3.939 λ (Good)=0.0656 failures/yr
b) λ (stormy)=4.202 λ (Good)=0.0525 failures/yr
c) λ (stormy)=6.594 λ (Good)=0.0458 failures/yr
d) λ (stormy)=20.16 λ (Good)=0.0403 failures/yr