A 31.8 mm H.S.S. drill is used to drill a hole in a cast iron block 100 mm thick at a cutting speed 20 m/min and feed 0.3 mm/rev. If te over travel of drill is 4 mm and approach 9 mm, the time required to drill the hole is
(a) 1 mm 40 s (b) 1 mm 44 s
(c) 1 mm 49 s (d) 1 mm 53 s