How to get surround sound wirelessly from AV receiver for less than 5 USD

This video shows how to get wireless audio connection from surround speaker output of AV receiver using BT transmitter and utilizing portable bluetooth speaker as rear surround speaker. It is cheap solution to run surround system without wires.
BT transmitter/receiver:
https://www.lazada.sg/products/i1641616737-s7712853237.html?urlFlag=true&mp=1&laz_trackid=2:mm_150190918_51702111_2010752174:clkgikoij1fsvv4q0s2s22&mkttid=clkgikoij1fsvv4q0s2s22
3.5 mm 3pin female extension cable:
https://www.lazada.sg/products/35mm-3-pin-4-core-male-female-audio-extension-cable-aux-single-head-line-stereo-3-4-wires-diy-audio-output-line-i2109275523-s11866979749.html?