Consider the region that lies between y=sinx and y=cosx on 0≤x≤4π and between y=cosx and the x-axis on 4π≤x≤2π. When this region is revolved about the x-axis, what is the exact volume of the resulting solid?
a) 4π2
b) 2π2
c) 8π2+4π
d) 4π2−8π