‘P’ will be the first part of the given sequence as it is introducing the central idea of the passage, that is, spending income so as to get whatever people want. RS will make a pair together as both of them are talking about ‘this scale of preferences’ referred in ‘S’ is use in the context of ‘personal scale of preferences’ in R. ‘Q’ will follow next as the pronoun ‘they’ is used in relation to ‘essential commodities’ referred in ‘S’. Hence, PRSQ is the correct sequence. Thus, option (b) is correct.