PQ is a chord of length $8\;cm$ of a circle of radius $5\;cm$ . The tangent at P and Q intersect at a point T. The length of TP is _________

Question

$\begin{array}{1 1} 20\;cm\\ \frac{20}{3}\;cm \\10\;cm \\\frac{10}{3}\;cm \end{array}$