Problem: the volume of the greatest sphere that can be cut off from a cylindrical log of wood of base radius 1 cm and height 5 cm is : 
Options: ['a ) 3 / 4 ∏', 'b ) 4 / 3 ∏', 'c ) 5 ∏', 'd ) 5 / 9 ∏', 'e ) none']
b