Return the sum of the specified column of the 2D array nums. The columnToSum parameter is the column that should be summed. If the columnToSum does not exist in nums, return -1.

Important Note: Copy the following two methods into the window and don't change 
array2DRowAverage.  CodingBat does not allow 2D array parameters, so this method is 
accepting the number of rows, number of columns, and a 1D array.  The first method takes 
this information and creates a 2D array named nums that you will be using. The columnToSum 
parameter is the column that should be summed.  Enter your code into method 
array2DColumnSumB:

public int array2DColumnSum(int rows, int cols, int[] array, int columnToSum)
{
	int[][] array2D = new int[rows][cols];
	int idx = 0;
	for (int r=0; r<rows; r++)
	{
		for (int c=0; c<cols; c++)
		{
			array2D[r][c] = array[idx];
			idx++;
		}
	}
	return array2DColumnSumB(array2D, columnToSum);
}

public int array2DColumnSumB(int[][] nums, int columnToSum) { 
		
}