$($iv$)$ Write a function, computePrice that receives two parameters: the first one is a character variable indicating the size of the pizza $(S,M$ or $L)$ and the second an integer variable indicating the number of toppings on the pizza. It then computes the cost of the pizza and returns the cost as a floating point number according to the rules:

$,$ Small pizza $=R50+R5\mathrm{.}50$ per topping

$,$ Medium pizza $=R70+R6\mathrm{.}50$ per topping

$,$ Large pizza $=R90+R7\mathrm{.}50$ per topping