Are Letters in the Second String Present in the First?

Create a function that accepts a list of two strings and checks if the letters in the second string are present in the first string.

Examples

letter_check(["trances", "nectar"]) ➞ True

letter_check(["compadres", "DRAPES"]) ➞ True

letter_check(["parses", "parsecs"]) ➞ False

Notes

• Function should not be case sensitive (as indicated in the second example).
• Both strings are presented as a single argument in the form of a list.
• Bonus: Solve this without RegEx.