Cheapest to deliver (CTD) Treasury bond

The speaker discusses the cheapest to deliver treasury bond.  He suggests that the role of the conversion factor is to make the short seller in the treasury bond futures indifferent in delivery among various different government bonds.  The short seller will maximize their profit by selecting the cheapest to deliver bond.  Essentially, a short seller of a bond futures contract will want to deliver the bond with the cheapest cost for them.  The speaker reviews the formula that one could use to calculate this.