Possibly all 10, but this is extremely rare (all 10 kids on the nomination slate would have to be 3Q, which is statistically improbable). 2 kids from my district already have an appointment and it isn't even March yet.
Appointments in each district vary from only 1 to all 10...depending on the candidates from it and what West Point needs.
Not all 10 unless that district has absolutely nobody at the Academy already. You have to factor in how many cadets from that district are already there as there are only so many allowed at the Academy at any given time.
Don't confuse how many applicants can be charged to a MOC with how many nomination sources are out there. Each MOC can have 5 cadets at any one time, which is typically one per year and then every fifth year he would have two openings. Applicants can compete for multiple nominations, ROTC, Service Connected, etc and they can also be pulled of the NWL. In theory, all 10 could get an appointment but reality is usually somewhere in the middle.