γreal=γapp.+γvessel So (γapp.+γvessel)glass=(γapp+γvessel)steel⇒153×10−6+(γvessel)glass=144×10−6+(γvessel)steel Further, (γvessel)steel=3α=3×(12×10−6)=∘C36×10−6⇒153×10−6+(γvessel)glass=144×10−6+36×10−6⇒(γvessel)glass=3α=∘C27×10−6⇒α=∘C9×10−6