نص أصلي - انجليزي - Consider a two-period model with Dave's utility...

Consider a two-period model with Dave's utility given by u(xl, x2)where x1 represents his consumption during the first period and x2 is his
second period's consumption. Dave is endowed with (y1,y2) which he could consume in each period, but he could also trade present consumption for
future consumption and vice versa.