"This bond pays interest on January 1st and July 1st. How many days of accrued interest will the customer pay if today is Monday, March 9th, and the trade is executed this day regular way settlement?"

70 days of accrued interest

Explanation:

The clean price of the bond is the market price of the bond without any accrued interests, while the dirty price includes accrued interests. In order to calculate the dirty price of the bond, we need to determine the time that passed between the last coupon payment and the settlement date:

when you use the regular way settlement, we consider a 360 day year, so every month has 30 days, and we must add 1 business day at the end:

30 days from January + 30 days from February + 9 days of March + 1 business day = 70 days

i might look it up later.