An electron is trapped in a deep well with a width of 0. 3 nm. If it is in the state with quantum number n = 3, what is its kinetic energy?
a. 6. 0 x 10⁻¹⁸ J
b. 1. 8 x 10⁻²⁷ J
c. 6. 7 x 10⁻¹⁹ J
d. 2. 0 x 10⁻¹⁸ J