public static int[][] readBoard( Scanner sc ) Uses the provided Scanner to read the board and return a 2D integer array with the appropriate values. Input should be 9 rows of values with 9 characters each. These characters will be 1-9 to indicate a fixed number in the starting board, or a - (dash) to indicate an empty location. A value of 0 indicates an empty space in the returned array. Should return null if the board was invalid (contains invalid characters or does not contain enough values.) Example input: