The HUKTS university is opening an IMOS $7020$ course in the Spring semester. The cost for each seat planned in the class is $300$ HKD $($e$.$g$.,$ instructor, TA$,$ equipment etc$).$ The tuition charged for each enrolled student is $1000$ HKD$.$ If the planned seats are unfilled, it has a salvage value of zero. Suppose the students$$ demand for the IMOS $7020$ course follows a normal distribution with mean of $120$ and standard deviation of $30.$