Estimate the heat per unit depth (perpendicular direction to the face of paper), W/m by free convection if a 25 cm vertical plate, with a surface temperature maintained at 50°C, is suspended in atmospheric air at 25°C. Use $h = 5 \frac{W}{m^2 \circ C}$.
HINTS:
Note that $h$ is given.
Calculate $q$, and then heat flow per unit depth is $q \cdot L = 31.5$ W/m.