I'm not really sure if this is a valid argument or not. We are supposed to solve it using the modern square of opposition and the wording is just confusing me!
a. It is false that some dogs are not mammals.
Therefore, it is false that no dogs are mammals.
Valid or invalid?
In the traditional square, two propositions are said to stand in the relation of subalternation when the truth of the first ("the superaltern") implies the truth of the second ("the subaltern"), but not conversely.
And since (traditionally), ...
Validity in arguments are assessed. The modern square of opposition functions are given.