In a food web,each successive trophic level has

$A$ plant receives $10000 \ J$ of energy from the sun. The amount of energy that will be present at the third trophic level is $:-$ (in $J$)

The transfer of energy from organisms to organisms in a natural community establishes

If plants have $1000\,J$ of energy,how much energy will reach the trophic level of a lion (in $,J$)?

The driving force of any ecosystem is

Assertion $A$: Heat energy is available for the functioning of a system.
Reason $R$: Some amount of energy is lost during energy transformation.
Which option is correct for Assertion $A$ and Reason $R$?