A rectangular wooden beam 8 meters long must have a cross-sectional perimeter of 0.60 meter. If the cross section has width w meters and height h meters with 2w+2h=0.60, which width w maximizes the volume of the beam?
a) w=0.25 m
b) w=0.10 m
c) w=0.15 m
d) w=0.20 m