[DNSB]

Here's what I am using for the time estimates. Please note that you may have to change the 24000 and 23300 to match the estimates closer to your reading speed. The mod function returns the remainder so it's not useful here. I.e., your 372,000 word book has a remainder of 0 when divided by 12 and a remainder of 0 when divided by 10.

I set those numbers as guesstimates years back and have never bothered to change them though they do yield times that are longer than my average reading time for a book. Basically, they are a reading speed of 400 wpm multiplied by 60 for the lower number of hours and about 3% less than 400x60 for the larger number of hours.

Edit: attached image
Edit2: commented on using Mod function