from typing import List


def base_determinant(matrix: List[List[int]]) -> int:
    """
    Find determinant of a 2 x 2 matrix.
    """
    if (len(matrix[0]), len(matrix)) != (2, 2):
        raise ValueError(f"Matrix mismatch: Not 2 x 2 matrix.")

    return (matrix[0][0] * matrix[1][1]) - (matrix[0][1] * matrix[1][0])