What is wrong with my script?

I have a script that I have made from a tutorial and it says that unity does not know the definition of velocity what is wrong? the script is below

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class MouseController : MonoBehaviour {

public float forwardMovementSpeed = 3.0f;

public float jetpackForce = 75.0f;

private Rigidbody2D rb2d;

void Start () {
	rb2d = GetComponent<Rigidbody2D>();
}

void Update () {

}

void FixedUpdate () 
*{Vector2 newVelocity = rigidbody2D.velocity;*
	newVelocity.x = forwardMovementSpeed;
	***rigidbody2D.velocity = newVelocity;***
	bool jetpackActive = Input.GetButton("Fire1");

	if (jetpackActive)
	{
		rb2d.AddForce(new Vector2(0, jetpackForce));
	}
}

}

You created a variable called rb2d to reference the rigidbody2d component. But then in FixedUpdate you’re trying to use an undeclared reference called rigidbody2D instead. So those lines should read:

Vector2 newVelocity = rb2d.velocity;
 ...
 rb2d.velocity = newVelocity;