Explanation

We know that plant only utilisexd 1-2% of total energy incident on earth. In the given dustion 100000 $Kcal/m^{2}/yr$ salar radiation is incident on earth. So plant producer utilize 1% of 100000 $kcal\ m^{2}/yr$ and that 1% is $= \frac{100000 \times 1}{100} = 1000\ kcal/m^{2}/yr$ And from produces to the next level only 10% will goes, so $\frac{1000 \times 10}{100} = 100\ kcal/m^{2}/yr$ will be transferred to primary consumer which is called secondary production