Internal wall box lintel
 

I wish to remove a wall between the kitchen and dining-room. This wall is
3.6m wide and 2.6m high, is a single brick thick, has a door to one side and
supports a single story wall above. I want to make an opening about 3.3m
wide and 2.3m high. There is only about 100mm of wall at the side of the
door. How can I calculate the minimum end bearing length for an Expamet box
lintel?