I need to calculate the formulas of a certain pipe section that consists of a shell and a branch (see image below):

The areas are demarcated with hatching and named: A

_{fs I}, A

_{fb I}, A

_{fb II}, A

_{fs II}, A

_{p I}, A

_{p II}

The basic Formulae are pretty easy to get to, with regards to just splitting the area members in different shapes, like for instance A

_{fb I}:

A

_{fb I}= (L x B) + (0.5 x b x H)

Where this is easy to see that the shape members are a rectangle and a triangle(with a 90 degree angle inside)

What I am struggling to determine is the individual items which will have their own formulae, like for instance B = e

_{as}= d

_{o}- d

_{i}

Anyone willing to help please do.

Thank you in advance!