A small surface of area A = 1 cm² emits radiation as a blackbody at 1800 K. Determine the rate at which radiation energy is emitted through a band defined by 0 ≤ ϕ ≤ 2π and 45 ≤ θ ≤ 60°, where θ is the angle a radiation beam makes with the normal of the surface and f is the azimuth angle.