A plastic sleeve of outer radius $r_0=1$ $mm$ covers a wire (radius $r=0.5\:mm$) carrying electric current. Thermal conductivity of the plastic is $0.15 W/m-K$. The heat transfer coefficient on the outer surface of the sleeve exposed to air is $25 W/m^2-K$. Due to the addition of the plastic cover, the heat transfer from the wire to the ambient will

1. increase
2. remain the same
3. decrease
4. be zero