Challenge 2: A with-Expression Leaving the Original Untouched — Possible Solution
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Program.cs:

public record Product(string Name, decimal Price);

var original = new Product("Widget", 9.99m);
var discounted = original with { Price = 7.99m };

Console.WriteLine(original);
Console.WriteLine(discounted);

Output:

    Product { Name = Widget, Price = 9.99 }
    Product { Name = Widget, Price = 7.99 }

Explanation:
`original with { Price = 7.99m }` creates an entirely new Product
instance -- discounted -- copying Name unchanged from original and
replacing only Price. original itself is never modified; it still
reports its original 9.99 price after the with-expression runs,
confirming with produces a genuinely separate object rather than
mutating the source record in place.

WHY THIS WORKS AS AN ANSWER
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This demonstrates the chapter's own core with-expression claim
directly -- a new instance is produced with one property changed,
while the original remains completely unaffected.