Trauma & Orthopaedic Society Conference Ticket Sale

1. Early bird tickets (orthosoc members) - £8
2. Early bird tickets (non-orthosoc/ external university members) - £10
3. General tickets (orthosoc members) - £12
4. General tickets (non-orthosoc/ external university members) - £15

Can we have total 20 available links for the early bird tickets and can that be automatically disabled once 20 tickets have sold out from the first 2 options? 
 
Max total ticket links at 60 (max capacity for our event).