Help with script

![public float sensitivityX = 0.5f;
public float sensitivityY = 0.5f;
public float sensitivityXR = 0.5f;
public float sensitivityYR = 0.5f;
public float vol;
public float smoothTime;
public float sensetivityTime;

	void Update () {
		float rotationX = Input.GetAxis ("MouseX") * sensitivityX;
		float rotationY = Input.GetAxis ("MouseY") * sensitivityY;
		sensitivityYR = Mathf.SmoothDamp (sensitivityYR, rotationY, vol, smoothTime * Time.deltaTime);
		sensitivityXR = Mathf.SmoothDamp (sensitivityXR, rotationX, vol, smoothTime * Time.deltaTime);
		float rotValue = Quaternion.Euler (sensitivityYR, sensitivityXR, 0);
		transform.localRotation = Quaternion.Slerp(transform.localRotation,rotValue,sensetivityTime*Time.deltaTime);


The next error line in the console tells you exactly what the issue is:

error CS1620: Argument #3’ is missing ref' modifier

So the line should read:

sensitivityYR = Mathf.SmoothDamp (sensitivityYR, rotationY, ref vol, smoothTime * Time.deltaTime);

Also, there is another error in the code. ‘rotValue’ should be a Quaternion instead of a float.