completed in time?

$30$ monrhs. Deter$-$

$20.$ A machine can operate for an average of $10$ weeks before it needs to be overhauled, a process which takes two days. The machine is operated five days a week. Compute the availability of this machine. $($Hint: All times must be in the same units.$)$

$(2)48$ months,

$21.$ A manager must decide between two machines. The manager will take into account each