A vertical line passing through the point $(h,0)$ intersects the ellipse ${{{x^2}} \over 4} + {{{y^2}} \over 3} = 1$ at the points $P$ and $Q$. Let the tangents to the ellipse at $P$ and $Q$ meet at the point $R$. If $$\Delta \left( h \right)$$$=$ area of the triangle $PQR$, ${{\Delta _1}}$$$= \mathop {\max }\limits_{1/2 \le h \le 1} \Delta \left( h \right)$$ and ${{\Delta _2}}$$$= \mathop {\min }\limits_{1/2 \le h \le 1} \Delta \left( h \right)$$, then ${8 \over {\sqrt 5 }}{\Delta _1} - 8{\Delta _2} =$