答案：(a) $\$400$ (b) $15\%$
- 手袋的成本
$\begin{array}{cl}
= & \$560\div(1+40\%) \\
= & \$400
\end{array}$ - 盈利百分率
$\begin{array}{cl}
= & \dfrac{\$460-\$400}{\$400}\times 100\% \\
= & 15\%
\end{array}$
