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If $ f\left( x \right) =\cfrac { 1 }{ x } +\cfrac { 5 }{ \sqrt { x } } $, the value of $f^{ \prime }\left( 4 \right)=$

$-\cfrac { 3 }{ 8 } $

$-\cfrac { 1 }{ 4 } $

$\cfrac { 3 }{ 8 } $

$\cfrac { 11 }{ 4 } $