If i have a cylinder that has a rectangle port in the side of the cylinder, i need to find the area of that port.

the cylinder has an inside diameter of 66mm
port width - 30mm
port height - 13mm
top left corner radius - 0.2mm
top right corner radius - 0.4mm
bottom left corner radius - 0.3mm
bottom right corner radius - 0.5mm
I figured out, how to work out the area with using one corner radius, but i need to figure out how to calculate the port area using four different corner radii. I also included the chordal width, as the layout was unfolded out on paper.
Code:
Chordal width =SIN(RADIANS(port width*180)/(3.1415927*cylinder bore dia))*cylinder bore dia
Port Area (using 1 radii & chordal width)
=(port height*chordal width)-3.1415927*((corner radius)*(corner radius/4))-corner radius
I am thinking i should average the radii, first perhaps
