How many rooms whose capacity is less than 50 does the Lamberton building have?
return buildings ;return rooms of  #1 ;return #2 where  #1 is Lamberton ;return capacities of  #3 ;return #3 where  #4 is lower than 50 ;return number of  #5
['select', 'project', 'comparative', 'project', 'comparative', 'aggregate']