\[\boxed{\text{459\ (459).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{в)}\ \frac{1}{3} < a < \frac{1}{2}\]
\[\frac{40}{120} < a < \frac{60}{120}\]
\[a = \left\{ \frac{41}{120};\frac{45}{120};\frac{50}{120};\frac{55}{120};\frac{59}{120} \right\}\]