Problem $4$:

A project utilizing experienced drillers will require drilling and blasting of low$-$silica dolomite, average efficiency $50-$min hour. No field drilling tests were conducted. It is proposed to use a $6\mathrm{.}5-$in B downhole drill at $350$psi. The drills to be used have a single$-$pass capability of $18ft$ and take steel in $20-ft$ lengths. The blasting pattern will be a $1111-ft$ grid with $2ft$ of subdrilling. On the average, the specified finish grade is $24ft$ below the existing ground surface. Determine the drilling production, assuming it takes $20$ min to change a $6\mathrm{.}5-$in$.$ downhole hammer. Find the following:

$1)$ total drill depth $($ft$)$

$2)$ drill time $($min$)$

$3)$ change steel time $($min$)$

$4)$ blow hole time $($min$)$

$5)$ move drill time $($min$)$

$6)$ align steel time $($min$)$

$7)$ change bit time $($min$)$

$8)$ total drill time per each hole $($min$)$

$9)$ operating rate $($ft$/$min$)$

$10)$ hourly production including production efficeincy $($ft$/$hr$)$