a$)$ What are the three main types of computer network based on their sizes? Explain each one of them in detail. $(2\mathrm{.}5$ Points$)$

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b$)$ As we all know, the internet can be considered a network of networks. Modern$-$world internet is different than the initial network shared by a group of people known to each other. Considering the advancement of modern internet. Draw the structure and explain the possible elements impacting the structure of the internet, including access ISPs, regional ISPs, IXP, content providers, and Tier $1$ ISPs.$(2\mathrm{.}5$ Points$)$

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