If $V_{mc}=$ cutting speed for the minimum cost and $V_{mat}=$ cutting speed for the minimum time, then for high efficiency range, which one of the following is true for cutting speed?
(a) Between $V_{mat}$ and $V_{mc}$
(b) $\leq V_{mc}$
(c) $\geq V_{mt}$
(d) $\leq V_{mat}$