How much steam must be condensed to convert $1kg$ liquid nitrogen at $-250C$ to a gas at $20C$ if there are no heat losses? Specific heat of liquid nitrogen $=57\mathrm{.}12kJ(kmolK{)}^{-1}$ and latent heat of vaporization $=5575kJkmo{l}^{-1}.$ Specific heat of nitrogen gas $=29\mathrm{.}12kJ(kmolK{)}^{-1}.$ Boiling point of nitrogen is $-196C.$ Latent heat of vaporization of water $=2260kJk{g}^{-1}.$ Molecular mass of nitrogen is $28gmo{l}^{-1}.$