All units in mm

Given:

$cs=20\frac{m}{\text{m}\text{i}\text{n}}=20000\frac{mm}{\text{m}\text{i}\text{n}}$

depth $of$ cut $(roughing)=1\mathrm{.}5mm$

depth $of$ cut $(finshing)=0\mathrm{.}5mm$

one $(1)$ pass for facing

$f_p=0\mathrm{.}165\frac{mm}{\text{r}\text{e}\text{v}}$

$f_f=0\mathrm{.}125\frac{mm}{\text{r}\text{e}\text{v}}$

Required:

MT $($Minimum$)$

Original diameter$=60$ mm

Original length$=120$ mm

Diameters $(60,50,35,21)$

Lenghts $(30,20,30,40)$

Solve by sections. Thanks.