Write a function that does the following operations: adding, subtracting, dividing, or multiplying values. It is simply referred to as variable operation variable. Of course, the variables have to be defined, but in this challenge the variables will be defined for you. All you have to do is look at the variables, do some string to integer conversions, use some if conditionals, and combine them based on the operation.

Think about how to do it. Is there a function? It is simpler than you think. The numbers and operation will be given as a string, and you should return the value as a string as well.

Examples

operation("1", "2", "add" ) ➞ "3"

operation("4", "5", "subtract") ➞ "-1"

operation("6", "3", "divide") ➞ "2"

Notes

• The numbers and operation will be given as a string, and you should also return the value as a string.
• If the answer is "undefined", return "undefined" (e.g. dividing by zero).