$Q$#$3$

$($a$)$ Evaluate the traces in electron$-$muon scattering given

$]$

$[u(P_3+m)$

$($b$)$ Evaluate the traces given as:

$T_r[{}_1({}_b+m_b)tilde({)}_2({}_a+m_a)]$

where ${}_1={}_5{}^{}$ and ${}_2={}^v$