Gear hobbing produces more accurate gears than milling because in hobbing

Teeth of internal spur gears can be accurately cut in a

The cutting tool are being tried for an operation. Tailors tool life equation for them are as follows
$$\eqalign{ & HSS\,\,tool\,:\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,V{T^{0.1}} = 200 \cr & Carbide\,\,tool\,:\,\,\,\,\,\,\,V{T^{0.35}} = 500 \cr} $$
Find out the break even speed above which the carbide tool will be economical.

In an orthogonal cutting test on the following data were obtained
Uncut chip thickness $$=0.25mm,$$ Cutting speed: $$60m/min,$$ Tool rake angle: $$0$$ Chip thickness $$0.75mm,$$ Cutting force : $$900$$ $$N$$, Thrust force : $$450$$ $$N$$

Calculate the shear angle, total power in making the cut and coefficient of friction between the chip tool interface.