4. (10 pts.) This question focuses our inverted V diagram for kerogen maturation on a different topic. Ethylene is the most important industrial organic chemical in the world. Various processes and feedstocks are used to manufacture ethylene. One of them involves the cracking of so-called gas oils. A typical gas oil is 82% C with an atomic H/C 1.27. This process is always accompanied by the formation of ethylene cracker tar, a high- molecular weight, very viscous, highly aromatic liquid. (a) Why is the formation of this tar inevitable? (b) And, why is it aromatic?