Given the task definition and input, reply with output. In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: a right triangle with sides 3 cm , 4 cm and 5 cm is rotated about the side of 3 cm to form a cone . the volume of the cone so formed is
Options: ['a ) 12 cm 3', 'b ) 15 cm 3', 'c ) 16 cm 3', 'd ) 20 cm 3', 'e ) none']
a