A 280 g cork ball with a charge of 300 microc is suspended

Question

Solve the all parts of given problem:

Problem: A 2.80 g cork ball with a charge of 3.00 µC is suspended vertically on a 0.750 m long light string in the presence of a uniform, downward-directed electric field of magnitude E = 1.00 x 10⁵ N/C. If the ball is displaced slightly from the vertical, it oscillates like a simple pendulum.

Part A: Determine the period of this oscillation.

Part B: By what percentage does the inclusion of gravity affect the period?

Please show work on how to solve!