Complete and balance each of the following nuclear equations:
a. $\mathrm{Bi}-209+\mathrm{Cr}-54 \longrightarrow ?+{ }_{0}^{1} n$
b. Np-237 undergoes alpha decay.
c. ${ }_{2}^{4} \mathrm{He}+{ }_{95}^{241} \mathrm{Am} \longrightarrow ?+2{ }_{0}^{1} n$