$\displaystyle a= \frac{5}{2 }$\displaystyle a= \frac{5}{2 }

$\displaystyle a= \frac{2}{5 }$\displaystyle a= \frac{2}{5 }

$\displaystyle a= \frac{3}{2 }$\displaystyle a= \frac{3}{2 }

$\displaystyle a= \frac{2}{3 }$\displaystyle a= \frac{2}{3 }