Find the probability for finding a free particle within \(dq\) of a point \(q\)


 * 1) Find the probability in terms of \(q\): \(P(q) = \left|\langle q_F | q_I \rangle \right|^2 = \frac{m}{2\pi\hbar t}\)
 * 2) Find the probability in terms of \(p\).
 * 3) Find the velocity of the particle: \(v = \frac{q}{t}\)
 * 4) Find the momentum of the particle: \(p = \frac{mq}{t}\)
 * 5) Find \(dp\): \(dp = \frac{mdq}{t}\)
 * 6) Set \(P(p)dp = P(q)dq\).
 * 7) Expand this using the above identities: \(P(p)\frac{mdq}{t} = \frac{m}{2\pi\hbar t}dq \)
 * 8) Simplify: \(P(p) = \frac{1}{2\pi\hbar}\)