$B = \dfrac{121^{2} . 24^4 . 49^3}{77^5 . 342}$
$⇔ B = \dfrac{(11^2)^2 . (3 . 2^3)^4 . (7^2)^3}{(7.11)^5 . 2 . 3^2 . 19}$
$⇔ B = \dfrac{11^4 . 3^4 . 2^{12} . 7^6}{7^5 . 11^5 . 2 . 3^2 . 19}$
$⇔ B = \dfrac{1 . 3^2 . 2^{11} . 7}{1 . 11 . 1 . 1 . 19}$
$⇔ B = \dfrac{3^2 . 2^{11} . 7}{11 . 19}$
$⇔ B = \dfrac{129024}{209}$.