Challenge 2: A Product Price HashMap — Possible Solution
====================================================================

use std::collections::HashMap;

fn main() {
    let mut prices: HashMap<String, f64> = HashMap::new();
    prices.insert(String::from("Mouse"), 24.99);
    prices.insert(String::from("Keyboard"), 59.99);
    prices.insert(String::from("Monitor"), 199.99);

    match prices.get("Keyboard") {
        Some(price) => println!("Keyboard: ${}", price),
        None => println!("Keyboard not found"),
    }

    match prices.get("Webcam") {
        Some(price) => println!("Webcam: ${}", price),
        None => println!("Webcam not found"),
    }
}

WHY THIS WORKS AS AN ANSWER
------------------------------
Three insert() calls populate the HashMap<String, f64> with the
required product-name-to-price mappings, matching this chapter's own
HashMap example pattern.

prices.get("Keyboard") returns Some(&59.99) since that key exists —
the match's Some(price) arm extracts and prints it directly.

prices.get("Webcam") returns None since that key was never inserted —
handled by the match's None arm rather than causing any error or
panic. Because get() returns Option<&V> (per this chapter), there is
no way to accidentally treat a missing key as if it held a real price
— both outcomes must be explicitly handled, exactly the same
discipline Chapter 6's Option<T> enforced everywhere else.