John's camera broke so he decided to rent one for 4 weeks.  It was a $5000 camera and the rental fee was 10% of the value per week.  His friend who was there when it broke agreed to pay 40% of the rental fee.  How much did John pay?
The rental fee is 5000*.1=$<T>multiply(5000, 0.1)=500.0 per week
So it cost 500*4=$<T>multiply(500, 4)=2000
His friend pays 2000*.4=$<T>multiply(2000, 0.4)=800.0
So he pays 2000-800=$<T>subtract(2000, 800)=1200
