In $($a$)$ and $($b$),$ a car is going through the top and the bottom of a hill, respectively. The velocity is $10\frac{m}{s}$ in both cases. The radius of the curvature of the hill is $100$ m in both $($a$)$ and $($b$).$ The car $($including the person in it$)$ has a mass of $500$ kg $.$ Determine the normal force acting upon the car in $($a$)$ and $($b$).$