It is estimated that the cost of running a small car is $150 per week, based on driving 15 000km per year. Taking the cost to be normally distributed with a standard deviation of $10 per week, answer the following.

(a) What proportion of small cars cost more than $170 per week to run?

(b) What proportion of small cars cost between $120 and $180 per week to run?

(c) You want to be 95% certain that the weekly cost of running your small car will not exceed your budgeted amount. How much should you budget?