A (7,4) block code is generated by mapping messages [a1a2a3a4] to codewords [a1a2a3r3a4r2r1], where $r_1 = a_1 + a_3 + a_4$, $r_2 = a_1 + a_2 + a_4$, and $r_3 = a_1 + a_2 + a_3$. Given two messages $m_1 = 1000$ and $m_2 = 0101$, the corresponding codewords $W_1$ and $W_2$, respectively, are: