Answer
$E = 6.81 eV$
Work Step by Step
From the probability equation,
$ P_1 = \frac{1}{e^{E_1 - E_F/kT} + 1}$
Rearrange the equation
$ E = E_F + kT ln (P^{-1} - 1)$
where
$E_F $ for copper is 7.00 eV
$k = 8.62 \times 10^{-5} eV/K$
$T = 1000K$
Probability occupied by electron $P= 0.900$
Substitute all values into equation
$ E = 7.00 eV + (8.62 \times 10^{-5} eV/K) (1000K) ln (\frac{1}{0.900} - 1)$
$E = 6.81 eV$
