Given the following question, rubric and students' answer: question: 
'''
Simple JavaScript Calculator
Instructions:

1. Open your preferred code editor or browser-based environment, such as JSFiddle or CodePen.

2. Create an HTML file and include the necessary tags for a basic HTML structure (<!DOCTYPE>, <html>, <head>, <body>). Add a <script> tag inside the <head> or at the end of the <body> to write your JavaScript code.

3. In the JavaScript section, declare the following variables:

num1: A number variable to store the first operand.
num2: A number variable to store the second operand.
operation: A string variable to store the chosen operation (addition, subtraction, multiplication, or division).
result: A number variable to store the result of the operation.

4. Write a function called performOperation that takes num1, num2, and operation as arguments. This function should perform the specified operation using a conditional statement (e.g., if-else or switch statement) and return the result.

5. Add test code for performOperation function with different values for num1, num2, and operation. For example:

num1 = 5, num2 = 3, operation = "add" should return 8.
num1 = 7, num2 = 2, operation = "subtract" should return 5.
num1 = 3, num2 = 4, operation = "multiply" should return 12.
num1 = 10, num2 = 2, operation = "divide" should return 5.

6. Display the result of each test case using console.log() or by appending the result to the HTML document using DOM manipulation.

7. Create a simple user interface with input fields and buttons to allow users to enter their own values for num1, num2, and operation. The operation should be performed when the user clicks the "Calculate" button. The result should appear on the screen.  

'''
rubric:
'''
Rubric for Simple JavaScript Calculator Activity:

2. HTML structure and JavaScript integration (2 points):

Correctly includes the basic HTML structure (DOCTYPE, html, head, body).
Adds a script tag in the appropriate location (head or end of body) for JavaScript code.

3. Variable declaration and initialization (2 points):

Properly declares and initializes the required variables (num1, num2, operation, result).

5. Function implementation (3.5 points):

Creates a function called performOperation that takes num1, num2, and operation as arguments.
Utilizes a conditional statement (if-else or switch) to perform the specified operation.
Returns the correct result based on the provided operation.

6. Function testing and result display (2.5 points):

Tests the performOperation fun Write exactly 3 paragraphs each separated with two new lines answering this question. The 2nd paragraph must start with "identity".
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