question: Find the year and semester when offers the largest number of courses.
#1 return semesters 
#2 return courses that  #1 offer 
#3 return number of  #2 for each #1 
#4 return #1 where #3 is  the  largest 
#5 return years 
#6 return courses offer in #5 
#7 return number of  #6 for each #5 
#8 return #5 where #7 is  the  largest 
#9 return #8 ,  #4