What is the electric field at a point in the cavity a

Question

Use the following to answer question 1-3:

A positive total charge Q is distributed on a conducting spherical shell (shaded area) with inner radius R₁ and outer radius R₂. A Particle with charge q is placed at the center of the cavity. Here, q=2.00 μC, Q = 8.50 μC, R₁ = 4.00 cm, and R₂ = 7.00 cm.

What is the electric field at a point in the cavity, a distance r = 1.50 cm from the center?

What is the electric potential at r = 5.00 cm from the center?

Find the potential at r = 1.50 cm from the center.