Let $f\left( x \right) ={ x }^{ 4 }+a{ x }^{ 3 }+b{ x }^{ 2 }+cx+d$, for that $a,b,c,d$ are constants. If $f\left( 1 \right) =1993,\quad f(2)=3986,\quad f(3)=5979$. Calculate the value of $\frac { 1 }{ 4 } [f(11)+f(-7)]$.

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