First Before Second Letter

You are given three inputs: a string, one letter, and a second letter.

Write a function that returns True if every instance of the first letter occurs before every instance of the second letter.

Examples

first_before_second("a rabbit jumps joyfully", "a", "j") ➞ True
# Every instance of "a" occurs before every instance of "j".

first_before_second("knaves knew about waterfalls", "k", "w") ➞  True

first_before_second("happy birthday", "a", "y") ➞ False
# The "a" in "birthday" occurs after the "y" in "happy".

first_before_second("precarious kangaroos", "k", "a") ➞ False

Notes

• All strings will be in lower case.
• All strings will contain the first and second letters at least once.