def left_top_submatrices(left_top_tuple: tuple, n_half: int) -> tuple:
    """
    Calculates the coordinates of the top left corner of the four submatrices
    and returns these as four tuples of two coordinates
    """
    left, top = left_top_tuple
    M00 = (left, top)
    M01 = (left + n_half, top)
    M10 = (left, top + n_half)
    M11 = (left + n_half, top + n_half)
    return (M00, M01, M10, M11)