How many DATA steps does the program below contain?          
 

         data profit;                            
            infile sales;                        
            input year 1-4 expenses 6-10         
                  revenue 12-16;                 
         run;
         proc means data=profit;                 
         run;
         proc print data=profit;                 
         run;
         proc plot data=profit;                  
            plot revenue*year;                   
         run;