SQL 2012 user CAL Questions

I tried to setup a SQL 2012 server with 5 SQL client PC. Those 5 PC use same application to connect to SQL server with same network user account. It's a 24/7 manufacture enviroment each PC use by 3 operators with 3 shifts. How many user CAL I need to buy?

1. (5 PC with same SQL account) 5 user CAL?
2. (5 PC x 3 user) 15 user CAL?
3. (5 PC x 3 user x 3 shift) 45 user CAL?