Ferdinand has decided to buy a car. He has to choose between a diesel car and a petrol car. The diesel car costs R105000 more than the petrol car. However, it can travel 15 kilometres per litre, whereas the petrol car can only travel 12 kilometres per litre. Also, diesel costs R76.50 per litre, and petrol costs R86.40 per litre. If he buys a diesel car, how many kilometres must he drive before the savings in fuel covers the extra price of the diesel car?
If the number in the center is the sum of all other numbers, find the value of a. (Clarification: In the figure, the terms containing a are products of a with single digit numbers.)