Walker, Halliday & Resnick — Electric Potential: Problem 67

67 A plastic disk of radius $R = 64.0 \text{ cm}$ is charged on one side with a uniform surface charge density $\sigma = 7.73 \text{ fC/m}^2$, and then three quadrants of the disk are removed. The remaining quadrant is shown in Fig. 24-51. With $V = 0$ at infinity, what is the potential due to the remaining quadrant at point $P$, which is on the central axis of the original disk at distance $D = 45.0 \text{ cm}$ from the original center?