Twitter Inc is poised to agree a sale to Elon Musk for around $43 billion in cash, the price the chief executive of Tesla Inc has called his “best and final” offer for the social media company, people familiar with the matter said. Twitter may announce the $54.20-per-share deal later on Monday once its board has met to recommend the transaction to Twitter shareholders, the sources said. It is always possible that the deal collapses at the last minute, the sources added. Musk, the world’s richest person according to a tally by Forbes, is negotiating to buy Twitter in a personal capacity and Tes…