A machine in your factory sews red sweaters and blue t$-$shirts $($on the same machine$).$The demand for red sweaters is $18$ per hour and the demand for blue t$-$shirts is $6$ per hour.Red sweaters can be sewn at a rate of one sweater every $1$ minute. Blue t$-$shirts can be sewn at a rate of one t$-$shirt every $2$ minutes. Assume $100\%$ yield and $100\%$ availability of the machine.What is the capacity of this machine $($in units per hour$),$ assuming it produces according to the product mix given above?