Index: docs/P3-UseCaseModel/UseCase0004.md
===================================================================
--- docs/P3-UseCaseModel/UseCase0004.md	(revision 9577c7944ff24ddc9145ff6637494f07d87c3dd4)
+++ docs/P3-UseCaseModel/UseCase0004.md	(revision 0cee8ec194e8e518624fcec244168861a6a7de27)
@@ -10,8 +10,9 @@
 
 1. Trader chooses "Place market BUY order".
-2. System lists the available markets with their latest price:
+2. System lists the active markets, numbered, with their latest price:
 
    ```sql
-   SELECT m.id, c.symbol, m.quote_currency, COALESCE(lp.price, 0)
+   SELECT m.id, c.id, c.symbol, m.quote_currency,
+          COALESCE(lp.price, 0) AS price
      FROM project.markets m
      JOIN project.crypto  c  ON c.id = m.crypto_id
@@ -20,14 +21,10 @@
     ORDER BY c.symbol;
    ```
-3. Trader enters a market symbol, e.g. `ETH`.
-4. System resolves the market and looks up the latest price:
+3. Trader picks the market by its number in the listed markets, e.g. `2` (BTC).
+4. System takes the chosen row's market id and crypto id from the list (no lookup by
+   symbol) and looks up the latest price:
 
    ```sql
-   SELECT m.id, c.id AS crypto_id, c.symbol, m.quote_currency
-     FROM project.markets m
-     JOIN project.crypto c ON c.id = m.crypto_id
-    WHERE upper(c.symbol) = upper($1) AND m.is_active = true;
-
-   SELECT price FROM project.v_latest_prices WHERE market_id = $2;
+   SELECT price FROM project.v_latest_prices WHERE market_id = $1;
    ```
 5. Trader enters a quantity.
@@ -91,5 +88,5 @@
 If `available_balance < notional`, the entire transaction rolls back and system shows "Insufficient funds: need X, have Y."
 
-### Alternate flow 4a — market not found
+### Alternate flow 3a — number not in the list
 
-If the entered symbol does not match any active market, system shows "market X not found" and returns to the authenticated menu without opening a transaction.
+If the entered number is not one of the listed market numbers, system shows "Invalid choice, enter a number from 1 to N." and returns to the authenticated menu without opening a transaction.