How can I add time to a timer on an object collision?

In my game I have a timer that will countdown from 10, but if the player hits these orbs then I want to have an additional 5 seconds be added to the timer.

Here is my timer code.

using UnityEngine; using System.Collections;

public class Timer : MonoBehaviour {

 public float time = 11;

  IEnumerator Do() {
     yield return new WaitForSeconds(3);
     Application.LoadLevel(Application.loadedLevel);
 }

 // Use this for initialization
 void Start () {
 
 }
 

 void Update () {
 
     time -= Time.deltaTime;
 }

 void OnGUI(){
     if (time > 1) {
         GUI.Label (new Rect (100, 100, 200, 100), "" + (int)time);
     } 

     else {
         GUI.Label (new Rect (100, 100, 200, 100), "Game Over");
         StartCoroutine(Do());
     }
 }

}

Here is my collsion.

using UnityEngine; using System.Collections;

public class Des : MonoBehaviour {

 void OnTriggerEnter(Collider other) {
     Destroy(other.gameObject);

 }

}

Also I was looking for a way to make the timer not be able to go past 20 seconds. For that i was thinking about something like

if(time >= 20){ time = 20; }