It is decided in a study project that a twist$-$drill of $30$ mm diameter with point angle of

$118$ will be used to assess machinability of a ductile material. A student writes a CNC

command to execute the drilling operation is G$90$ G$01$ Z$??$ F$20.$ The datum is defined on the

top surface of the work material and the approach distance is $3$ mm $.$ Then, to achieve a

cylindrical hole depth of $40$ mm $,$ the Z coordinate to be provided in the CNC command, in

mm $,$ is: $($a$)-49\mathrm{.}013($b$)45\mathrm{.}013($c$)40($d$)$ none of these.