Explanation:
r = 250 ( thousand) and r = 180 + 35 log4 (x) <====base 4 LOG
sooooo 250 = 180 + 35 log4(x) find 'x' thousands
(250 -180)/35 = log4 (x)
2 = log4(x) these are exponents of 4 ...anti log base 4:
4^2 = 4^(log4 x)
16 = x
But x is thousands of $ (per the question info)
so $ 16 000