Objective question in Electric Potential

A thin spherical conducting shell of radius R has a charge q. Another charge Q is placed at the centre of the shell. The electrostatic potential at a point P a distance frac{R}{2} from the centre of the shell is a) frac{(q+Q)}{4pi ,{{varepsilon }_{0}}}frac{2}{R} b) frac{2Q}{4pi {{varepsilon }_{0}}R} c) frac{2Q}{4pi {{varepsilon }_{0}}R}-frac{2q}{4pi {{varepsilon }_{0}}R} d) frac{2Q}{4pi {{varepsilon }_{0}}R}+frac{q}{4pi {{varepsilon }_{0}}R}