10-1/3. 1 minute 18 seconds including the time it took me to go get the DMG. All you do is look on any line of the table on p.38. I like 8th level. A CR 2 is 300 XP. A CR 3 is 400 XP. Add them all up.
600 - (2) CR2
800 - Worgs (2) CR3
800 - Manticore (1) CR5
1500 - Hobgoblin Veterans (5) CR2
600 - Minotaur (1) CR4
1200 - Hobgoblin Sorcerer (1) CR6
=
5500. Look for 5500 on that 8th row. CR 10 is 4800 XP and CR 11 is 7200 XP. Ergo, 10-1/3. I checked it
here and got 10.4, but I knew it would work. It really is that simple if they'd only realized it.