Exercise 1: Classifying IaaS vs. PaaS vs. SaaS — Possible Solution
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(a) "We rent virtual machines and manage our own OS patching and web
    server config."
    -> IaaS. Per the chapter's own table, IaaS is defined by the
    customer managing the OS, runtime, application, data, and
    configuration themselves -- exactly what "we manage our own OS
    patching and web server config" describes. The provider only
    handles the physical hardware, virtualization, and network layer
    underneath the rented VM.

(b) "We just push our application code and the platform handles
    scaling and runtime patching automatically."
    -> PaaS. The customer here only manages the application code and
    data -- the platform (not the customer) is handling the OS,
    runtime, and scaling, which is exactly the PaaS row of the
    chapter's table. This is the defining PaaS trade: less control
    over the underlying environment, in exchange for not having to
    manage it at all.

(c) "We use a web-based CRM tool and never think about servers at
    all."
    -> SaaS. The customer isn't managing any part of the technical
    stack at all -- only their own data and who on their team has
    access to the tool -- matching the chapter's SaaS row exactly
    ("everything else, end to end" managed by the provider).

WHY THIS WORKS AS AN ANSWER
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Each scenario description maps directly onto one row of the chapter's
IaaS/PaaS/SaaS table by identifying WHO is doing the OS/runtime/
scaling work described in the scenario -- the customer in (a), the
platform in (b), and neither (just the vendor) in (c). This is exactly
the diagnostic question the chapter's table is built to answer: "how
much of the stack does the customer actually touch here?"