Liquid ammonia is being transported in an insulated tube with an outer diameter of D₁ = 4 cm and the outer tube surface temperature is uniform at T₁ = 0°C. Exposure to high concentration of gaseous ammonia can cause lung damage. To prevent gaseous ammonia from forming and leaking out, ammonia is transported in its liquid state inside the tube. In addition, the tube is enclosed by an outer concentric cylindrical shield with a diameter of D₂ = 8 cm, which gives a vacuumed gap in between the tube and the shield surfaces. Keeping the surface temperature of the shield uniform at 10°C or lower would prevent the liquid ammonia to vaporize. Both the outer tube and the shield surfaces have the same emissivity of 0.33. The tube is situated in a surrounding at where the natural convection heat transfer coefficient is 3 W/m² ∙ K, and both natural convection and radiation heat transfer occur at the outer shield surface. To keep the ammonia inside the tube in its liquid state, determine the surrounding temperature that would maintain temperatures of the outer tube and the shield at the specified values.