Create a matrix and find the largest value of each row and column

I have a question in a program Basically the program says the following: Finding the largest value of each row, of each column and the largest of the entire matrix, is a 4x7 matrix. Actually the program is a menu with more options but I already have all, I just do not know how to find the largest value of the row and column, the highest value of the whole matrix also I get the only problem is with the columns and rows.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ULTIMOEXAMEN
{
    class Examen
    {
        public float[,] matriz;


        public void iniciar()
        {
            matriz = new float[4, 7];
            for (int f = 0; f < 4; f++)
            {
                for (int c = 0; c < 7; c++)
                {
                    Console.Write("Ingrese posicion [" + (f + 1) + "," + (c + 1) + "]: ");
                    string linea;
                    linea = Console.ReadLine();
                    matriz[f, c] = float.Parse(linea);
                }
            }


        }
        public void menu()
        {
            Console.WriteLine("ELEGIR UNA OPCION: ");
            Console.WriteLine("1- SUMAS");
            Console.WriteLine("2- MAYOR");
            Console.WriteLine("3- ESCALAR");
            Console.WriteLine("4- SALIR");

            switch (Console.Read())
            {
                case '1':
                    //SUMA DE FILAS
                    for (int f = 0; f < 4; f++)
                    {
                        float suma = 0;
                        for (int c = 0; c < 7; c++)
                        {
                            suma += matriz[f, c];
                        }
                        Console.WriteLine("FILA " + f + " = " + suma);
                    }
                    //SUMA DE COLUMNAS

                    for (int c = 0; c < 7; c++)
                    {
                        float suma = 0;
                        for (int f = 0; f < 4; f++)
                        {
                            suma += matriz[f, c];
                        }
                        Console.WriteLine("COLUMNA " + c + " = " + suma);
                    }

                    break;

                case '2':

                    //EL MAYOR DE TODA LA MATRIZ
                    float mayortodo = 0;
                    float mayor = matriz[0, 0];
                    for (int f = 0; f < 4; f++)
                    {
                        for (int c = 0; c < 7; c++)
                        {
                            if (matriz[f, c] > mayortodo)
                            {

                                mayor = matriz[f, c];
                                mayortodo = mayor;

                            }
                        }
                    }
                    Console.WriteLine("EL ELEMENTO MAYOR DE LA MATRIZ ES:" + mayortodo);

                    //EL  MAYOR DE CADA FILA
                    float mayorfila = 0;
                    float mayor2 = matriz[0,0];
                    for( int f=0; f<4; f++)
                    {
                        for (int c=0; c<7; c++)
                        {
                            if(matriz[f,c]>mayorfila)
                            {
                                mayor2 = matriz[f, c];
                                mayorfila = mayor2;
                            }
                        }
                    }
                    Console.WriteLine("EL ELEMENTO MAYOR DE LA FILA ES: " + mayorfila);
                    break;

                case '3':
                    break;

                case '4':
                    System.Environment.Exit(4);
                    Console.ReadKey();
                    break;
            }

        }

        static void Main(string[] args)
        {
            Examen ex = new Examen();
            ex.iniciar();
            ex.menu();
            Console.ReadKey();

        }
    }
}