Let the constant state of supply of heat per unit time =λ. So according to the first condition. λt1=mc×100⇒mλ=t1100C...(i), and according to the second condition, λt2=mLf⇒mλ=t2Lf...(ii). By (i) and (ii) t1100C=t2Lf⇒101cal×100=55Lf⇒Lf=550calg−1