Answer:
I think it's 336 I'm not entirely sure though
70*300
=70(100+100+100)
=7,000+7,000+7,000
=21,000
Set 7x-4 and 31 equal to each other
7X-4=31
Add four to both sides
7X=27
X=3
The answer is D
Given that

, it has PDF

and thus CDF

The 25th percentile is the value

such that

. We have