How to merge multiple 'having' clause relation in rails 3

If i remove any one of scopes having clause then the above action works perfectly . Is there any way to like- @model = Model.vacant_list(daterange) and then remove the active record relation and then apply @model.amenity_type(term). I tried lots of things but didnt find any solution for this..... Full question listed here http://stackoverflow.com/questions/6986561/how-to-merge-multiple-having-clause-relation-in-rails-3