ΔUAB​=40J as process is isochoric.ΔUBC​=+50(WBC​=−50J)UC​=UA​+ΔUAB​+ΔUBC​=1650For CA process,QCA​=−60JΔUCA​+WCA​=−60−90+WCA​=−60⇒WCA​=+30JThe graph given is inconsistent with the statement BC may be adiabatic and CA cannot be like isobaric as shown, as increasing volume while rejecting heat at same time.