Each weekend Sid notices that his van'rate of fuel consumption is the same every weekend.He leaves home with his fuel tank nearly empty so he has to fill up at the local petrol station first.He sells only enough so that his takings are $100 plus the cost of fuel used since filin up, based on the price paid at the petrol station.On the first weekend Sid bought petrol at 1.46 a litre so he decided to charge 85c per icecream.He travelled 328km and sold 152 icecreams to make his required total.On the 2nd weekend Sid bought petrol at 1.40 and sold icecreams 80c ea.On the 3rd weekend petrol was 1.45 so Sid increased the price, sold 13 less icecreams and used 3L less fuel than the 2nd weekend.On the 4th wkend petrol was 1.50 perlitre.Sid raised the price again,this time by twice last week. He went 360.8km and sold 140 icecreams.

a) What was the price of ice-creams in week 4.

b) What was the price of ice-creams in week 3.

c) How many litres of petrol did he use on the 2nd weekend?

Thanks.