From the given shovels: $18,20,25,45$ and $60m^3$ bucket capacity, select

the appropriate one for a bauxite mine using shovel$-$truck production

equipment. The production data are: required production in bank: $15,000$

tons$/$shift; shift operating time: $7$ hr ; availability of the shovel: $50mi\frac{n}{h}r.$

muck: medium digging; cycle time $34$ sec ; bank density: $2\mathrm{.}0$ tons$/$yd$3$;

loose density: $1\mathrm{.}30$ tons$/$yd$3$; swing angle: $120.$