Cost of house extension (ground floor only) in greater sydne

Hi guys we have a 3 year old double storey house in sydney. We now want to
1. Either convert the alfresco (has main slap and main roof) into a room, then add an alfresco and another room infront of that

2. Add 2 rooms on the other side, not touching the alfresco

Considering no easements, plenty of space both sides and even after the extension where will be 2-3 setbacks from the boundary line, flat block, good access, does not need plumbing/bathrooms to this area,

Roughly thinking of adding 35m2 in 2 rooms. What cost are we looking at? Has anyone done this?

Thanks