$$\begin{gathered} \text{ Consider the circle }{\mathrm{x}}^2+{\mathrm{y}}^2-4\mathrm{x}-2\mathrm{y}+\mathrm{c}=0\text{ whose centre is }\mathrm{A}(2,1)\text{. If the point }\mathrm{P}(10,7)\text{ is such that the line} \\ \text{segment PA meets the circle in }\mathrm{Q}\text{ with }\mathrm{PQ}=5 \text{ then }\mathrm{c}\text{ is equal to } \end{gathered}$$