Common case slips

Ten minutes on the topic's own four common mistakes: a feminine -а noun left in the nominative where it stands as an object, an accusative form wrongly used as the sentence's own subject, an ending invented for an inanimate masculine noun that needs none, and the nominative reached for instead of the vocative when calling out to someone. Build sentences around loving and buying something, catching each slip in turn, before the unit's own listening and reading put the whole topic to work.