The return on total assets is calculated as -
Return on total assets = (Net income + Interest expense) / Average total assets
Average total assets = (Total assets of year 1 + Total assets of year 2) / 2
Average total assets =( ($ 600,000 + $ 60000 + $ 900,000) + ( 560,000 + $ 40000 + $ 700000) ) /2
Average total assets = $ 1,430,000
Return on Total assets = ( $ 150,000 + $ 20,000) / $ 1,430,000
Return on Total assets = 11.9%