1. Explain how you would do simple accounting with a database
2. Point out which indices you'd create for performance
3. Show how the "double entry" part of double entry accounting is about the indices
2. For performance, you would create indices based on the accounts in the transaction table, so you could easily check what's going on e.g. in your groceries account or how much you spent at the supermarket.
3. Double entry accounting was formalized in the 15th century, way before computers became a thing, but bound paper books were already somewhat affordable. The way you'd do accounting is like this: During the business day, you would write down your transactions as they happen, into a scrapbook, similar to the transactions table mentioned above. At the end of the day, you'd do the "double entry" part, which means you take your "index" books where each book is about one account and you transcribe each transaction from your scrap book into the two books of the two accounts that are mentioned in the transaction, e.g. if you spent $10 from your groceries account into the supermarket account, you'd double enter that transaction both into your "groceries" book and into your "supermarket" book. Then, when you want to check on how much you spent at the supermarket in a particular month, you could easily look it up in the supermarket book (this would be very tedious when using the scrap book). These account centered books are like the indices in the database mentioned above.
So the double entry part is about clever index building for making it easier and faster to understand what's going on in your accounting system.
It happens so often I even wrote a script to switch to the MacBook internal speakers then back to the headphones.
I've used wired headphones before (and the Sony even has a wired option), but I didn't like how the cord was constantly getting the the way of my arms.
edit: Another big gripe is with the Bluetooth codec itself, and how the quality changes depending on if the mic is active.