Final answer:
A notaphile, who collects paper currency, is one type of numismatist, an individual who collects and studies a broader range of currency, including paper money. Thus, notaphiles are encompassed within the broader category of numismatists.
Step-by-step explanation:
In the context of collecting and studying, a notaphile is a person who collects paper currency, such as banknotes, while a numismatist is a person who collects and studies currency, which typically includes coins, tokens, paper money, and related objects. Therefore, the correct inference about notaphiles and numismatists is that a notaphile is one type of numismatist (option a), because notaphiles focus specifically on paper currency, which is a subset of what numismatists study. Option b is incorrect because notaphiles have a more specialized focus, and option c is not verifiable without more specific data about the number of individuals in each hobby. Lastly, option d is incorrect as notaphiles do not focus on a type of currency ignored by numismatists; rather, they focus specifically on paper currency, which is indeed of interest to numismatists.