$$\begin{aligned} & a = \sqrt { 12 } - \sqrt { 8 } \\ & b = \sqrt { 27 } + \sqrt { 18 } \end{aligned}$$ Given that, what is the product a.b?\\ A) $4 \sqrt { 2 }$\\ B) $3 \sqrt { 3 }$\\ C) 4\\ D) 5\\ E) 6