Let S be the solid whose base is the region bounded by y=x and y=4x for 0≤x≤4. A cross section perpendicular to the x-axis at position x is a triangle whose height is three times its base, where the base equals the distance between the two curves at that x-value. What is the volume of S?
a) 544
b) 522
c) 5
d) 1522