ଯଦି \(\frac{2a}{7}, \frac{3a}{4}, \frac{2a}{3}, \frac{a}{7}, \frac{a}{8}, \frac{a}{2}\) ର ମଧ୍ୟମା \(\frac{11}{28}\) ଅଟେ, ତେବେ 'a'ର ମୂଲ୍ୟ ଖୋଜନ୍ତୁ।