Touch once to activate and touch again to deactivate gameObject using Renderer

Hi all I am trying to learn my way through Unity and have setup a scene

I have A as prefab (custom) and B (sphere) of which A has 2 sphere gameobject as child. When the scene starts A is hidden via renderer.

My aim is when B is touched A should get activated and when B is touched again A should get deactivated. I have manage to achieve the first part ( Touch B to activate A), but cannot get A to deactivate again.

Please help, the script follows

 using UnityEngine;
 using System.Collections;
 
 public class touchtest1 : MonoBehaviour {
 
     public Renderer A_mesh;
 
     public GameObject A_prefab;
 
     void Start() {
 
         A_mesh.GetComponent<Renderer>().enabled = false;
     }
 
     void Update () {
 
         RaycastHit hit = new RaycastHit();
         for (int i = 0; i < Input.touchCount; ++i) {
             if (Input.GetTouch (i).phase == TouchPhase.Began) {
 
             Ray ray = Camera.main.ScreenPointToRay (Input.GetTouch (i).position);
                 if (Physics.Raycast (ray, out hit)) {
 
                     if (hit.collider.name == "B") {
                 
                         Debug.Log ("hit B!!!!!");
 
                         A_mesh.enabled = true;
                         A_prefab.SetActive (true);
 
                     }
 
                 }
             }
         }
 
     }
 }