SelectTarget Does not exist Current Context

Hi there first of all i want to say i have been following BergZerg arcade tutorial on rpg game. But on tutorial 08-10 i ran into a problem as stated as the title. Here is the image on what the problem is

and here is the code

 using UnityEngine;

using System.Collections; using System.Collections.Generic;

public class targeting : MonoBehaviour { public List targets; private Transform selectedTarget;

 private Transform myTransform;

 // Use this for initialization
 void Start () {
     targets = new List<Transform>();
     selectedTarget = null;
     myTransform = transform;
     
     AddAllEnemies();
 
 }
 
 public void AddAllEnemies()
 {
         GameObject[] go = GameObject.FindGameObjectsWithTag("enemy");
     
         foreach(GameObject enemy in go)
                 AddTarget(enemy.transform);
 }
 private void SortTargetsByDistance()
 {
         targets.Sort(delegate(Transform t1, Transform t2)    
     { return    Vector3.Distance(t1.position, myTransform.position).CompareTo(Vector3.Distance(t2.position, myTransform.position));    });

 }
 public void AddTarget(Transform enemy)
 {
     targets.Add(enemy);
 }
 
 private void TargetEnemy()
 {
     if(selectedTarget == null)
     {
             SortTargetsByDistance();
             selectedTarget = targets[0];
     }
     else
     {
             int index = targets.IndexOf(selectedTarget);
         
             if(index < targets.Count - 1)
             {
                     index++;
             }
             else
             {
                     index = 0;
             }
             DeselectTarget();
             selectedTarget = targets[index];
             
     }
     SelectedTarget();
 }
 
 private void SelectTarget()
 {
         SelectedTarget.renderer.Marterial.color = Color.red;
     
     playerattack pa = (playerattack)GetComponent("playerattack");
     
     pa.target = selectedTarget.gameObject;
 }
 
 private void DeselectTarget()
 {
         selectedTarget.renderer.Marterial.color = Color.blue;
         selectedTarget = null;
 }
 
 // Update is called once per frame
 void Update () {
         if(Input.GetKeyDown(KeyCode.Tab))
         {
             TargetEnemy();
         }
 }

}