John sends his son to prep school.  It cost $20,000 per semester.  There are 2 semesters in the year.  How much does it cost to send the kid to 13 years of school?
It cost 20000*2=$<T>multiply(20000, 2)=40000 a year
So it cost 40,000*13=$<T>multiply(40000, 13)=520000
,000