Help : Change Textbox from Dropdown List through AJax and PHP

I need to get price from multidimentional array through ajax.
I have some thing like this. I have to select Day and type of paper through Dropdowns & then Display price where it intersect.

Day1 Day2
school 14.75$ , 13.75$
undergraduate 16.75$ , 15.75$
Master 18.75$ , 17.75$
PHD 21.75$ , 17.75$

<?php
$row = $_POST['day'];
$col = $_POST['type'];
$shop = array( array("school", 14.75 , 13.75),
               array("undergraduate", 16.75 , 15.75),
               array("Master", 18.75 , 17.75),
	       array("PHD", 21.75 , 17.75) 
             ); 
?>

PHP:

<form method="POST" name="selectionForm">
 <?php 
   echo "<b>Urgency</b><br>
    <select name='day' id='day' > 
	
	<option  name='Steak' value='0'>  
    Please Select</option>
    <option  name='Meat' value='1' >1 Day</option>
	<option  name='Chicken' value='2' >2 day</option>
    <option name='Sushi' value='3' >3 Day</option>
    </select>
    <br><br>

  
  <b>Writer Levels</b><br>
    <select name='type' id='type'> 
	
	<option  name='one' value='0'>Please Select</option>
    <option  name='two' value='1' >  
    High School $10.00</option>
	<option  name='three' value='2' >  
    College $12.00</option>
    <option name='four' value='3' >University $15.00 </option>
    </select>
    <br><br>";
	
	echo "<strong>Your total is:</strong>
    <input type='text' name='total' >.$shop[$row][$col].</input>";
  	
  ?>
    

PHP: