Exercise 1: A LoyaltyDiscount, Standard-Shipping Order — Possible Solution
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BUILDING THE ORDER, USING ONLY EXISTING CLASSES
------------------------------
    order = (OrderBuilder()
        .items_total(150)
        .weight(8)
        .discount_strategy(LoyaltyDiscount())
        .build())

No new classes were needed - LoyaltyDiscount already exists from this
chapter's own capstone code, and shipping_strategy() is deliberately
left uncalled, so OrderBuilder's own default (StandardShippingStrategy)
applies automatically.

HAND CALCULATION
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    discount = 150 * 0.10 = 15
    final    = 150 - 15   = 135
    shipping = 8 * 0.5    = 4
    total    = 135 + 4    = 139

VERIFYING AGAINST THE ACTUAL CODE
------------------------------
    Exercise 1 total: 139.0
    manual: 150 - 150*0.10 + 8*0.5 = 139.0

Both match exactly.

WHY NO SHIPPING STRATEGY CALL WAS NEEDED
------------------------------
This chapter's own OrderBuilder.__init__() sets
self._shipping_strategy = StandardShippingStrategy() as its default
before any builder method is even called - so an order that never
needs priority shipping doesn't have to mention shipping at all, and
still gets the correct standard-rate calculation.

WHY THIS WORKS AS AN ANSWER
------------------------------
The order is built entirely from this chapter's own existing classes,
using the builder's own default for the strategy that wasn't
explicitly set, and the result is verified against a step-by-step hand
calculation rather than only the final total.