In which of the choices given below, the cutting tool materials are placed in the ascending order of permissible cutting speed for machining of steel?

Tool life equation for two tools under consideration are as follows

$$\eqalign{ & HSS:\,\,\,\,\,\,\,\,\,\,\,\,\,V{T^{0.2}} = 150 \cr & Carbide:\,\,\,\,\,\,V{T^{0.3}} = 250 \cr} $$
Where $$V$$ is the cutting speed in $$m/min$$ and $$T$$ is the tool life in $$min.$$ The breakdown cutting speed above which the carbide tool will be beneficial is

A cylinder of $$25mm$$ diameter and $$100mm$$ length is turned with a tool, for which the relation $$V{T^{0.25}} = 55$$ is applicable. The cutting velocity is $$22m/min.$$ For a tool feed of $$0.046$$ $$mm/rev,$$ the number of tool regrinds required to produce $$425$$ cylinders is

A single point cutting tool with a nose radius of $$0.4$$ $$mm$$ was used to turn a component in a lathe employing a feed rate of $$0.3$$ $$mm/rev.$$ If the feed-rate is doubled, the ideal surface roughness (peak-to-valley height) produced on the component will increase by a factor of