How to fix error: symbol "grub_calloc" not found (grub rescue)

? SUBSCRIBE FOR MORE ( It&FREE!!! ) ? ? Thanks for watching and I&see you in the next one! ???COMMANDS:??? 1. sudo mount /dev/sda1 /mnt (see if your OS drive is sda1) 2. sudo apt-get install grub-pc -y (use this if you get modinfo file is missing) 3. sudo grub-install --root-directory=/mnt/ /dev/sda