In a certain code, words are encoded using the Atbash substitution (A↔Z, B↔Y, C↔X, ...). If "CERTAIN" is coded as "XVIGZRM" and "SEQUENCE" as "HVJFVMXV", how is "REQUIRED" coded?

Introduction / Context:
Atbash cipher maps each letter to its mirror in the alphabet: A↔Z, B↔Y, C↔X, etc. The examples confirm this exact mapping.

Given Data / Assumptions:

• CERTAIN -> XVIGZRM
• SEQUENCE -> HVJFVMXV
• We need the code for REQUIRED.

Concept / Approach:
Apply Atbash per letter: r->i, e->v, q->j, u->f, i->r, r->i, e->v, d->w.

Step-by-Step Solution:
R -> IE -> VQ -> JU -> FI -> RR -> IE -> VD -> WThus "REQUIRED" -> "IVJFRIVW".

Verification / Alternative check:
Testing random letters from the examples reproduces their given codes, validating the mapping.

Why Other Options Are Wrong:

• FJIVWVIR / VJIFWTRY / WVJRIFVI: sequences conflict with Atbash at multiple positions.
• None of these: Not required since a correct option exists.

Common Pitfalls:
Reversing the word instead of mirroring letters, or applying a Caesar shift. Atbash is a fixed one-to-one mapping.

Final Answer:
IVJFRIVW