Installing Broadcom b43 driver offline on HP Pavilion dv6.

My friend installed Ubuntu 18.04 on HP Pavilion dv6 but Wi-Fi did not work on the Broadcom wifi adoptor. Moreover Ethernet did not work.

I downloaded following files on my mobile phone and sent to him on WhatsApp:
b43-fwcutter_019-3_amd64.deb from packages Ubuntu 18.04.
broadcom-wl-5.100.138.tar.bz2 from iwfinger.com

This friend was not familiar with Linux commandline and I had to make many calls and WhatsApp messages to execute following instructions.
Keep the files on Home folder and open terminal.
$ sudo dpkg -i b43-fwcutter_019-3_amd64.deb
$ tar xfvj broadcom-wl-5.100.138.tar.bz2
$ sudo b43-fwcutter -w /lib/firmware broadcom-wl-5.100.138/linux/wl_apsta.o

Reboot.
It works.