The SUMSQ function syntax has the following arguments: Number1, number2, ... Number1 is required, subsequent numbers are optional. 1 to 255 arguments for which you want the sum of the squares. You can also use a single array or a reference to an array instead of arguments separated by commas.
THEY/THEIR (SINGULAR). Using the plural pronoun to refer to a single person of unspecified gender is an old and honorable pattern in English, not a newfangled bit of degeneracy or a politically correct plot to avoid sexism (though it often serves the latter purpose).
A singular subject (she, Bill, car) takes a singular verb (is, goes, shines), whereas a plural subject takes a plural verb. Example: The list of items is/are on the desk. If you know that list is the subject, then you will choose is for the verb. Rule 1. A subject will come before a phrase beginning with of.