Write the structure and give the IUPAC systematic name of an alkane or cycloalkane with the formulas

Question:

Write the structure and give the IUPAC systematic name of an alkane or cycloalkane with the formulas
(a) C8H18 that has only primary hydrogen atoms,
(b) C6H12 that has only secondary hydrogen atoms,
(c) C6H12 that has only primary and secondary hydrogen atoms, and
(d) C8H14 that has 12 secondary and 2 tertiary hydrogen atoms.