Based on the relationship between customer retention (CR) and customer life-expectancy (CL), what change in customer retention rate when average customer life increases from 4 years to 8 years? (the change in customer retention rate = customer retention rate with 4 years of average customer life - customer retention rate with 8 years of average customer life) a decrease of 50% an increase of 50% a decrease of 12.5% an increase of 12.5%