something seems missing but lets give a try
A machine's maintenance cost every day while producing one unit is m dollar and n cents. If the machine runs 7 days a week and produces r units, how much is the total maintenance cost of that machine for 7 days for r units?
in case you are saying that r units per day then then answer will be
USD 7.r. (100m+n)/100
but if you mean to say total r units production in 7 days-as this appears from your question then....
it will be r.(100m+n)/100
per unit per day maintainance cost of machine is usd (100m + n)/100
now total production for 7 days is r units... so production for 1 day will be r/7 units.
now per day cost of r/7 units per days will be r*(100m+n)/700
and for 7 days it will be r*(100m+n)/100
kindly correct me if I am wrong.