user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: pennyweight is part of what measurement system? 
Knowledge Triplets: Mass, measurement_unit.dimension.units, Pennyweight
m.0qplrls, dataworld.gardening_hint.last_referenced_by, Mass
Mass, measurement_unit.dimension.units, Planetary mass
Mass, measurement_unit.dimension.units, Ounce
Mass, user.avh.default_domain.ellerdale_topic.ellerdale_id, 0080-0198
Mass, measurement_unit.dimension.units, Earth mass
mass.noun.01, base.wordnet.synset.equivalent_topic, Mass
Mass, measurement_unit.dimension.units, Cental
grain.noun.05, base.wordnet.synset.part_holonym, pennyweight.noun.01
Mass, measurement_unit.dimension.si_base_unit, Kilogram
pennyweight.noun.01, base.wordnet.synset.lexname, noun.quantity
Mass, measurement_unit.dimension.units, Gram
Wired, base.yupgrade.user.topics, Mass
Troy weight, measurement_unit.measurement_system.weight_units, Pennyweight
Troy pound, measurement_unit.mass_unit.measurement_system, Troy weight
Mass, measurement_unit.dimension.units, Catty
Mass, base.schemastaging.context_name.pronunciation, g.125_l6gm1
Troy weight, measurement_unit.measurement_system.weight_units, Troy pound
Mass, measurement_unit.dimension.units, Troy pound
pennyweight.noun.01, base.wordnet.synset.hypernym, troy unit.noun.01
Mass, measurement_unit.dimension.units, Grain
Mass, measurement_unit.dimension.units, Microgram
pennyweight.noun.01, base.wordnet.synset.word, m.07pnbh6
Troy weight, measurement_unit.measurement_system.weight_units, Troy ounce
Mass, measurement_unit.dimension.units, Milligram
Mass, measurement_unit.dimension.units, Hundredweight
Mass, measurement_unit.dimension.units, Tael
Mass, measurement_unit.dimension.units, Tonne
Mass (Physics), base.skosbase.skos_concept.equivalent_topic, Mass
Mass, measurement_unit.dimension.units, MeV/c²
noun.quantity, base.wordnet.lexical_name.synsets, pennyweight.noun.01
Mass, measurement_unit.dimension.units, Solar mass
Mass, measurement_unit.dimension.units, Dram
Pennyweight, measurement_unit.mass_unit.weightmass_in_kilograms, 0.00155517384
m.07pnbh6, base.wordnet.word_sense.sense, pennyweight.noun.01
Mass, measurement_unit.dimension.units, Candareen
Ana Marie Cox, base.yupgrade.user.topics, Mass
Mass, measurement_unit.dimension.units, Stone
m.07vn7ph, base.yupgrade.user.topics, Mass
Mass, measurement_unit.dimension.units, Cash
Troy weight, measurement_unit.measurement_system.weight_units, Grain
ounce.noun.01, base.wordnet.synset.part_meronym, pennyweight.noun.01
Mass, measurement_unit.dimension.units, Long quarter
Mass, base.ontologies.ontology_instance.equivalent_instances, m.07nfbgl
pennyweight.noun.01, base.wordnet.synset.part_meronym, grain.noun.05
pennyweight.noun.01, base.wordnet.synset.syntactic_category, Noun
Mass, measurement_unit.dimension.units, Jupiter mass
troy unit.noun.01, base.wordnet.synset.hyponymy, pennyweight.noun.01
Mass, measurement_unit.dimension.units, Short quarter
pennyweight.noun.01, base.wordnet.synset.gloss, a unit of apothecary weight equal to 24 grains
Mass, measurement_unit.dimension.units, Planck mass
Mass, measurement_unit.dimension.units, Picul
m.075_7gq, base.yupgrade.user.topics, Mass
pennyweight.noun.01, base.wordnet.synset.part_holonym, ounce.noun.01
Mass, measurement_unit.dimension.units, Electron rest mass
m.07nfbgl, base.ontologies.ontology_instance_mapping.freebase_topic, Mass
Mass, measurement_unit.dimension.units, Atomic mass unit
troy.noun.01, base.wordnet.synset.equivalent_topic, Troy weight
Troy ounce, measurement_unit.mass_unit.measurement_system, Troy weight
Troy weight, symbols.namesake.named_after, Troyes
pennyweight.noun.01, base.wordnet.synset.equivalent_topic, Pennyweight
Mass, measurement_unit.dimension.units, Kilogram
Mass, measurement_unit.dimension.units, Pound
Mass, base.skosbase.vocabulary_equivalent_topic.equivalent_concept, Mass (Physics)
Pennyweight, measurement_unit.measurement_system.weight_units, Troy weight
Mass, measurement_unit.dimension.units, Long ton
Mass, measurement_unit.dimension.units, Troy ounce
Grain, measurement_unit.mass_unit.measurement_system, Troy weight
Mass, measurement_unit.dimension.units, Carat
Mass, measurement_unit.dimension.units, Short ton
Pennyweight, measurement_unit.mass_unit.measurement_system, Troy weight
Mass, measurement_unit.dimension.units, Mace
Troyes, symbols.name_source.namesakes, Troy weight

Answer: Troy weight