Heat absorbed means heat is extracted from source, i.e. Q must be positive.
This occurs along path A→B→C ∴ Heat added =ΔQABC=ΔUABC+ΔWABC =nCV(TC−TA)+3p0(2V0−V0) =n23R(TC−TA)+3p0 V0=23(nRTC−nRTA)+3p0V0 =23(pCVC−pAVA)+3p0V0 =23(3p02V0−p0V0)+3p0V0 =23×5p0V0+3p0 V0=221p0V0=10.5p0V0