Counting secondary or tertiary carbon atoms in a branched alkane

This type of question, asked 2 times: 11 May 2024 S2, 14 May 2024 S1. All 2 questions below, oldest first.

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Question 1
11 May 2024 S2
80 $What is the number of moles of secondary carbon atoms in n mole isopentane?$
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Question 2
14 May 2024 S1
65 $What is the number of moles of tertiary carbon atoms in a molecule of isobutane?$
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