Writing a function with multiple arguments

In the last exercise, you wrote a function that returns the first letter of a student's grades. However, you would like a function that can be used to extract any of the student's grades.

For each student, you have text data that looks like this:

grades = "XXXX"

Where the letters "XXXX" are the grades for the student in mathematics, history, science, and drama, respectively.

A single string of grades named mygrades and an array of grade strings named grades_array is available in your environment.