60 m2 = 645 ft2
90' x 40' = 3600 ft2
3600 - 645 = 2955 ft2
Give 455 ft2 over to parking and that leaves you with a footprint of 2500 ft2. Then presumably you must take into account boundary walls, etc. If you want to jam a house in there you could by those calculations (very best case scenario) conceivably have a house of maybe 4500ft2. I would be very surprised if this could be achieved though. Suffice to say that you could have an adequately-sized 2-storey house.