b
(b) Let \(10 - \sqrt {24} - \sqrt {40} + \sqrt {60} = {(\sqrt a - \sqrt b + \sqrt c )^2}\)

\( = a + b + c - 2\sqrt {ab} - 2\sqrt {bc} + 2\sqrt {ca} \)

\(a,b,c > 0\). Then \(a + b + c = 10,\)

\(ab = 6\), \(bc = 10,\)\(ca = 15\)

\({a^2}{b^2}{c^2} = 900\)==> \(abc = 30\) \(( \ne \pm 30)\).

So, \(a = 3,\,\,\,b = 2,\,\,c = 5\)

Therefore, \(\sqrt {(10 - \sqrt {24} - \sqrt {40} + \sqrt {60} )} = \pm (\sqrt 3 + \sqrt 5 - \sqrt 2 )\)