begin{equation}
begin{aligned}
textrm{Row I:} qquad & A = 1, quad j = 1, 2, ldots, N \
textrm{Row II:} qquad & A =
begin{cases}
2, & j = 1, 2, ldots, m, \
3, & j = m+1, ldots, N
end{cases} \
textrm{Row III:} qquad & A = 4, quad j = 1, 2, ldots, N
end{aligned}
end{equation}