Every 3 months the arena's musical equipment needs safety checking. look at a comparison of the last 4 years' service costs. mean range year 1 ? 630 ? 300 year 2 ? 672.50 ? 80 year 3 ? 751.25 ? 67 year 4 ? 597.50 ? 350 each year the service was carried out by a different company. in which year was the service costs the cheapest? which year's prices were the most consistent?