For example...

when you get level 1 group steel along with the +25% damage upgrade (I don't recall the exact numbers), then also get level 2 group steel with the +30% damage upgrade... does that mean you get both?? And how are they applied?

If you would normally do a damage of 10, is it...

A. Then you get 10 plus 25%, which equals 12.5... then 12.5 plus 30% which equals a total damage of 16.25 hit points damage?

B. Then you get 10 plus 55%, which equals 15.5 Hit Points damage?

C. Or, do you only get the damage benefit of the highest sword skill level... and therefore would only get 10 plus 30% for a total of 13 hit points damage?

Ultimately, I'm trying to figure out if it is beneficial to get all levels of damage increase from the sword skill levels, or just go to the highest level you can open up and get the increases at that skill level? (as it relates to similar increases such as damage, as described above)