To find result we have to mulitply oxygen produced by each day (by dividing [tex]2.6*10^2[/tex]by 12) by tree by number of trees., so we have 2.6*102:12=21.6- single tree/day [tex]21.6*3.9*10^11=8.45*10^12[/tex] (to the power of 12) - its our result.