I just need an explanation with the answer on number 23. Thanks

23) On the July 5 billing date, David had a balance due of $847.34 on his credit card. The 23) transactions during the following month were: July 6 Payment July 19 Charge: auto repair $336 August 1 Charge: clothing $137.79 $258.53 The interest rate on the card is 1.1% per month. Using the average daily balance method, find the finance charge on August 5 Fuly has 31 days)