a) \[A=\frac{4}{7.31}+\frac{6}{7.41}+\frac{9}{10.41}+\frac{7}{10.57}\]
\[\frac{1}{5}A=\frac{4}{35.31}+\frac{6}{35.41}+\frac{9}{50.41}+\frac{7}{50.57}\]
\[\frac{1}{5}A=\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57}\]
$\frac{1}{5}A=\frac{1}{31}-\frac{1}{57}$
$A=\frac{130}{1767}$
b) $B=\frac{7}{19.31}+\frac{5}{19.43}+\frac{3}{23.43}+\frac{11}{23.57}$
$\frac{1}{2}B=\frac{7}{38.31}+\frac{5}{38.43}+\frac{3}{46.43}+\frac{11}{46.57}$
$\frac{1}{2}B=\frac{1}{31}-\frac{1}{38}+\frac{1}{38}-\frac{1}{43}+\frac{1}{43}-\frac{1}{46}+\frac{1}{46}-\frac{1}{57}$
$\frac{1}{2}B=\frac{1}{31}-\frac{1}{57}$
$B=\frac{52}{1767}$