Given a 2D array of strings, which represents a letter matrix. Your task is to rotate this matrix 90 degrees clockwise and output the result.
If the matrix is 
R 7 I S
S K C A
1 1 S E.
What is the result?
Return your answer with format <<<list of values and symbols>>>, For example, <<<A,B,C,D>>> represents a 2D array.