Path A-D-K Length and Net Area
The path length, in this case, is the plate width (12") less three EFFECTIVE HOLE DIAMETERS plus two STAGGERS:
EFFECTIVE HOLE DIAMETER = bolt dia. + 1/16" for std hole + 1/16" damage allowance
One stagger is between holes A and D and has a pitch (s) of 3" and a gage (g) of 3"
The other stagger is between holes D and K and has a pitch (s) of 3" and a gage (g) of 6"
Path Length = 12" - (3 hole diameters)*(3/4" + 1/8") + (3")2/(4*3") + (3")2/(4*6") = 10.50 inches
The net area equals the path length times the plate thickness:
Net Area = (10.50")(.375") = 3.94 in2