I posted this priviously and get the answers from chegg but, did not explained how to fix the error am getting in php code. It says, "Notice: Undefined index: tax in .opt/lamoo/htdocs/HOMEW4/order_form.php on line 7. " I provided my code below in HTML and PHP. Please show your code and explain how to fix this error problem and why it is giving me error and show the output.

This is assignment requirements.

This my PHP code

This is my HTML

This the output am getting and it says line 7 error on php code. Why is this happening and I cant see the error.

In the second exercise, you will create an order form for user to fill in. You PHP script will process the order form and then compute how to charge user. Ex-2 Create an html such as the following which will ask the user to enter an order form. It will calculate the total based on the business logic: Total -Quantity Unit price-Discount+ Shipping cest This amount will then be used to calculate tax. The final result after plus tax will be divided by the number of payments entered by user The business logic for shipping handling cost is calculated as follows $5.00 for Slow and steady.. $995 for Put a move on it. $19.36 for I need it yesterday! Fill out this fom to caloelate the total cost Price: 100 Quastiry: 20 Discosut: 12 20 widget(s) at $100 price each plus a $5.00 shipping cost and a 8 perceat tax rate methed Sow and steady and steady 3.00 Shipping Number of paymests to make: 1 your $12 discouat, the total cost is $215244 over 1 moothly paymeats, that would be $2152.44 each l(100 20-12+5) *1.081/1 (1993 *1.081/1 2152.44 Fill out this form to calculate the total cost: Price: 100 Qusatity: 20 Disconnt: 12 Tax: 8-(%) Shippng nedodL need eyesterdam HWpice each plus a Number of payments to make: 2 20 widgetis) at $100 price each plusa $19.36 shipping cost and a percent tax rate. After your 512 discouut, the sotal cost is $21 method: I need over 2 mouthly paymeots, that would be $10839744 each 100 20-12+ 19.36)*1.081/2 [2007.36 1.08]/2 (2167.9488]/2 1083.9744