It is proposed to manufacture glass beads of 0.5mm by spraying them in 20 degree C air and allowing them to harden as they fall to the ground. Assume that the initial temp of the glass bead is 500 degrees C. The bead air heat coefficient h=324 W/m^2K. Thermal velocity is 3.8 m/s. Glass k= .81W/mK. Alpha=.0034 cm^2/s. The design requires that the centreline temp not exceed 40 degrees C. From what height should the bead be dropped? Also what is surface temp when centreline temp is 40 degrees C.?