$($b$)$ Compute the machining time drill four $10$ mm diameter holes and $50$ mm diameter hole in the flange as

shown in Figure QU$1.25$ mm diameter hole is drilled first before it is enlarged to diameter $50$ mm hole.

Take cutting speed $12\frac{m}{m}in$ feed for $10$ mm drill $0\mathrm{.}15m\frac{m}{r}ev$ for $25$ mm drill feed is $0\mathrm{.}17m\frac{m}{r}ev$ and

for $50$ mm diameter drill feed is $0\mathrm{.}3m\frac{m}{r}ev.$