What is the speed of heat radiation equal to?

$A$ perfectly black body is placed in an enclosure (furnace) at room temperature. Then:

Nearly $10 \%$ of the power of a $110\,W$ light bulb is converted to visible radiation. The change in average intensities of visible radiation,at a distance of $1\,m$ from the bulb to a distance of $5\,m$ is $a \times 10^{-2}\,W/m^2$. The value of '$a$' will be.

At a certain temperature for a given wavelength,the ratio of the emissive power of a body to the emissive power of a black body in the same circumstances is known as:

Which of the following statements does not hold good for thermal radiation?

$x$ joule of heat is incident on a body. Out of it, the total heat reflected and transmitted by it is $y$ joule. The absorption coefficient of the body is