3. As shown in Fig. 1.2, a sketch of facing on a Lathe is illustrated. Try to indicate and draw the cutting depth $a_p$, feed rate $f$, cutting thickness $h_o$, cutting width $b_o$ by using the primary sketch. If $a_p = 5mm$, $f = 0.3mm$, $k_r = 45^\circ$, try to calculate the cutting area $A_D$.