AP has many overlapping rules concerning when to use digits vs. spelling out numbers. In general, use digits for numbers 10 and higher; spell out below 10. Exceptions include ages (always use digits) and percentages (always use digits and the percent sign: 4%). Textbook: 17:5 & following
People are referred to using the relative pronouns “who” or “whom”: the students who left. Institutions, objects and other nonhuman things use the relative pronouns “that” and “which”: the company that owns the building. Textbook: 16:2.C
Companies, unions, schools and other institutions are considered singular; they take singular pronouns and verbs: Kent State is reopening its admissions process. Textbook: 16:2.D01