Rule 15. Amended and Supplemental Pleadings

(a) Amendments Before Trial.
    (1) Amending as a Matter of Course.  A party may amend its pleading once as a matter of course:
        (A) before being served with a responsive pleading; or
        (B) within 20 days after serving the pleading if a responsive pleading is not allowed and the action is not yet on the trial calendar.
    (2) Other Amendments.  In all other cases, a party may amend its pleading only with the opposing party’s written consent or the court’s leave. The
    court should freely give leave when justice so requires.
    (3) Time to Respond.  Unless the court orders otherwise, any required response to an amended pleading must be made within the time
    remaining to respond to the original pleading or within 10 days after service of the amended pleading, whichever is later.

. . .

(c) Relation Back of Amendments.
    (1) When an Amendment Relates Back.  An amendment to a pleading relates back to the date of the original pleading when:
        (A) the law that provides the applicable statute of limitations allows relation back;
        (B) the amendment asserts a claim or defense that arose out of the conduct, transaction, or occurrence set out — or attempted to be set
        out — in the original pleading; or
        (C) the amendment changes the party or the naming of the party against whom a claim is asserted, if Rule 15(c)(1)(B) is satisfied and
        if, within the period provided by Rule 4(m) for serving the summons and complaint, the party to be brought in by amendment:
            (i) received such notice of the action that it will not be prejudiced in defending on the merits; and
            (ii) knew or should have known that the action would have been brought against it, but for a mistake concerning the
            proper party’s identity.
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(d) Supplemental Pleadings.  On motion and reasonable notice, the court may, on just terms, permit a party to serve a supplemental pleading
setting out any transaction, occurrence, or event that happened after the date of the pleading to be supplemented. The court may permit
supplementation even though the original pleading is defective in stating a claim or defense. The court may order that the opposing party plead to the
supplemental pleading within a specified time.