Solve the all parts of given problem:
Problem: Two 10-cm-diameter charged rings face each other, 18cm apart. The left ring is charged to -30nC and the right ring is charged to +30nC.
Part A: What is the magnitude of the electric field at the midpoint between the two rings?
Part B: What is the direction of the electric field at the midpoint between the two rings?
Please show all work to find the magnitude of the electric field at the midpoint between the two rings.