when i try to change the spund on my mac book air it has a circle with a line though it how can i fix it

Press and hold the power button on your Mac for up to 10 seconds, until your Mac turns off.

Turn on your Mac and immediately press and hold Command (⌘) and R to start up from macOS Recovery.  

While in macOS Recovery, use Disk Utility to repair your startup disk.

If Disk Utility found no errors or repaired all errors, take either of these actions:

Reinstall macOS

Restore from a Time Machine backup

If you still need help, please contact Apple Support.

plz mark brainliest

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