How to Find the Sum of each Individual item / array out of range

Hey, I am new and I am working on a project for a point of sale software using Unity UI , just to learn to code and I used Buttons for each items in the Menu and they would give out a number when pressed then created a list to collect its price and name. 1. Now I am having problems with finding the total sum of all the items. 2. Getting an error for array out of range.

This is the script where I get the number and calculate the total, I am getting array out of range error in Line 60.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine.UI;
 
 public class OrderInfo : MonoBehaviour 
 {
     int iNumber; 
     MenuList menuList;
     public int iQuandity, oNumber;
     //OrderInspector orderInspector;
     double totalCost;
     GameObject orderins;
     OrderProcess itemList;
     CreateText newText;
     public Text[] meal = new Text[3];
     private double[] indiPrice;
     public bool buttonPressed;
     public double grandTotal;
 
    
     void Start()
     {
         orderins = GameObject.Find("Order Inspector");
         menuList = orderins.GetComponent<MenuList>();
         itemList = orderins.GetComponent<OrderProcess>();
         newText = orderins.GetComponent<CreateText>();
         iQuandity = 0;
                 
     }
     void Update()
     {
         indiPrice = new double[oNumber];
         buttonPressed = false;
         Debug.Log(oNumber);        
     }
 
     public void OrderProcess(int num)
     {
         //when the button is pressed it gives out an appropriate number
         iNumber = num;        
         iQuandity++;                                  
         itemList.mealNumber.Add(iNumber);
         buttonPressed = true;
         if (iQuandity == 1)
         {
             newText.TextCreator(iNumber);
             oNumber++;
             //menuList.gTotal.Add(TotalCost());
             //itemList.GrandTotal(TotalCost());
         }
         if (iQuandity > 1)
         {
             //itemList.GrandTotal();
         }
         newText.TextCreator(iQuandity, TotalCost());
         //itemList.GrandTotal(TotalCost());
         for (int i = 0; i < oNumber; i++)
         {
             **indiPrice[i] = TotalCost();**
             Debug.Log(indiPrice[i]);
         }                    
     }   
 
     public double TotalCost()
     {
         double total;
         total = iQuandity * menuList.iPrice[iNumber];
         return total;
     }
 }

Please help me out !!