One yardstick for measuring how steadily—if slowly—athletic performance has improved is the mile run. In 1957, the local record for the running of a certain distance was 3 minutes, 59.2 seconds, or 239.2 seconds. In the half-century since then, the record has decreased by 0.4 seconds per year. a.) Express the record time for the mile run, M, as a function of the number of years after 1957, x.
b.) If this trend continues, in which year will someone run a 3-minute or 180-second, mile?