Petra’s electricity supply company charges her a fixed quarterly sum plus a rate per unit for electricity used. In the most expe
nsive quarter last year (January to March), she used 2 000 units and her bill was $250. In the least expensive quarter (July to September), she used 600 units and her bill was $138. She is now adding extra insulation to her home which is expected to reduce her overall electricity consumption by 25%. What can she expect her January to March bill to be next year (if there are no increases in overall tariffs)? *
