Typically, in most office type buildings you will have 5.6K sprinklers. When you have storage densities between 0.20 gpm / sq ft and .34 gpm / sq ft, you must use a minimum 8.0K sprinkler. In storage areas with densities of >0.34, then you are required to use a sprinkler with a minimum of 11.2K.
There are many other variables that come into play when selecting the K-Factor for sprinklers.