Busbar Sizing for 100A Feeders With 35kA and 65kA Short Circuit Levels

Lets say we have two load feeder circuit both having same Load e.g 100 A . What will be the size of the busbar if one having short circuit level 35KA and second have 65KA...

Two busbar systems connected to two separate circuit breaker compartments, using a single circuit breaker. This arrangement is achieved using the same principles as described above, so the cost of this design can be quite high, however the cost of duplicating common equipment such as "circuit breakers(circuit breakers)":http://www.circuitbreakercity.com/ can be omitted. This system can provide onload transfer between busbars if a spare circuit breaker is available. However if no spare/transfer circuit breaker is available this system may not provide the option of on-load transfer.

My Dear my question is let say i have two different load circuits one having ampere rating 100 A and circuit B also having ampere rating 100 A but both having short circuit level is 35KA and 65KA how we calculate the bus bar size inside the panel for these two circuits which have same ampere rating but different short circuit rating