task-2: define a function named plot serial numbers to make a histogram of any dataframe of serial numbers. it should take one argument, a dataframe like obs with one column named serial number. it should plot a histogram of the values in the column using bins of width 10 ranging from 1 to 170 but return nothing. also, the plot must display appropriate x-label, y-label, and title. then, call that function to make a histogram of the serial numbers in the column serial number of the dataframe obs.
