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);

					}

				}
			}
		}

	}
}

Any pointers appreciated