65.0
This is because 4 is not a big enough number to round up, so you must round down. When it is 5 and over, you can round up.
C+A=342
$5C+$12A=$2,550
5C+5A=1710
5C+12A=2550
-7C=-840
C=120
5(120)+12A=2550
600+12A=2550
12A=1950
A=163
G(f(5)) = 0.5(10(5)) + 1 = 26
