Given a rows x cols binary matrix filled with 0's and 1's, find the largest rectangle containing only 1's and return its area.

• A 2D array of strings/integers matrix.

Input: matrix = [["1","0","1","0","0"],["1","0","1","1","1"],["1","1","1","1","1"],["1","0","0","1","0"]]
Output: 6