Time Complexity of Nested Loops

The process method is shown below. Assume that matrix is a 2D array with n rows and m columns, and that the maximum value of any element in matrix is k. What is the worst-case time complexity of the method?

public class VariableInnerLoop {
    public static void process(int[][] matrix) {
        for (int i = 0; i < matrix.length; i++){
            for (int j = 0; j < matrix[i].length; j++){
                for (int k = 0; k < matrix[i][j]; k++){
                    // constant operation
                    int dummy = k;
                }
            }
        }
    }
}