Problem getting a function to work

Im trying to get a function to work out national inusance based on the condition that more than £89 is earnt. I want a function that works out a sum so long as the number is more than 89 and if not it should enter 0.
K3=420

L3 needs to be worked out

The condition needs to be if K3>89 then SUM((K3-89)/100)*11 and if K3<89 then SUM=0

I m really stuck and would appreciate any help on this matter!
Many thanks
Chance

Perhaps this?

=(K3>89)*(K3-89)/100*11

fantastic, thanks guys! I was almost there just needed the last push at the end!
Your help is much appreciated!
Chance