Two cutting tools are being compared for a machining operation. The tool life equations are:
$\begin{array}{ll} \text{Carbide tool:} & VT^{1.6} = 3000 \\ \text{HSS tool:} & VT^{0.6} = 200 \end{array}$
where $V$ is the cutting speed in $m/min$ and $T$ is the tool life in $min$. The carbide tool will provide higher tool life if the cutting speed in $m/min$ exceeds
- $15.0$
- $39.4$
- $49.3$
- $60.0$