Answer
$N_0(E) = 1.59\times 10^{28} m^{-3}.eV^{-1}$
Work Step by Step
Use the formula
$N_0(E) = P(E)N(E) $
From the previous answer,
$N (E) = 1.77 \times 10^{28} m^{-3}.eV^{-1}$
and
$P(E) = 0.900$
so
$N_0(E) = (0.900)(1.77 \times 10^{28} m^{-3}.eV^{-1})$
$N_0(E) = 1.59\times 10^{28} m^{-3}.eV^{-1}$
