Define two new operations as follows:

$H?T =$ $ \cfrac{H}{3}-T^2 $ and $H§Y = $ $ \cfrac{Y}{3}-H^2 $,

Simplify $(Y§T)?$ $ [(\cfrac{T}{81})^\frac{1}{2} ]$.

Assume that $?$ and $§$ have equal priority as orders of operations but have lower priority than exponents.

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