An undiscovered planet many light years from earth has one

Question

Problem: An undiscovered planet, many light years from Earth, has one moon in a periodic orbit. This moon takes 1560 × 10³ seconds (about 18 days) on average to complete one nearly circular revolution around the unnamed planet. If the distance from the center of the moon to the surface of the planet is 295.0 × 10⁶ m and the planet has a radius of 3.50 × 10⁶ m,

Part A: Calculate the moon\'s radial acceleration?

Any help would be greatly appreciated! Thank you so much!