A steel bar with a diameter of (D) is turned at a feed of (f) with a depth of cut of (d). The rotational speed of the workpiece is (N). What is the material removal rate (MRR) in (mm³/s)?
a. (π ⋅ D ⋅ f ⋅ N)
b. (π ⋅ D ⋅ f ⋅ N/4)
c. (π ⋅ D ⋅ d ⋅ N/4)
d. (π ⋅ D ⋅ d ⋅ N/2)
