Answer:
-2
Just put the point to -2.
12,540 / 570,000 = x / 460,000
cross multiply
570,000x = 5768400000
x = 5768400000 / 570,000
x = 10,120 <=== tax on 460,000
Given that

, it has PDF

and thus CDF

The 25th percentile is the value

such that

. We have