make-a-function-that-does-arithmetic

Make a function that does arithmetic!

Given two numbers and an arithmetic operator (the name of it, as a string), return the result of the two numbers having that operator used on them.

a and b will both be positive integers, and a will always be the first number in the operation, and b always the second.

The four operators are "add", "subtract", "divide", "multiply".

A few examples:

arithmetic(5, 2, "add")      => returns 7
arithmetic(5, 2, "subtract") => returns 3
arithmetic(5, 2, "multiply") => returns 10
arithmetic(5, 2, "divide")   => returns 2.5

ArithmeticFunction.arithmetic(5, 2, "add")      => returns 7
ArithmeticFunction.arithmetic(5, 2, "subtract") => returns 3
ArithmeticFunction.arithmetic(5, 2, "multiply") => returns 10
ArithmeticFunction.arithmetic(5, 2, "divide")   => returns 2

Try to do it without using if statements!