It has been determined that in Costa Rica 20% of families are lower class; Meanwhile, the percentage of middle and upper class families must be determined. Of upper class families, 90% usually leave the country by the end of the year, 30% of middle class families and 5% of lower class families do the same. The probability that a randomly chosen middle-class family who happened to leave the country at the end of last year was 0.4. Determine the percentage of upper class families in Costa Rica