Wide flange design with a slotted gusset plate

Hi,

This is follow up on a thread that was posted earlier.

I have a connection detail as shown below. The connection is a slotted gusset wide flange connection. Calculating the capacity of the wide flange member,

1) Can I use to entire area of the wide flange with consideration of shear lag, and reduction area due to slot to resist the force or
2) Just use the highlighted blue area (WT section) for force resistance

Thanks