Equation 7 represents the 2-coverage area near the border line. We calculate A5, which is one of the exact 3-coverage areas, in Equation 8. The exact 4-coverage area is computed by using Equations 9.

Equation 7 represents the 2-coverage area near the border line. We calculate A5, which is one of the exact 3-coverage areas, in Equation 8. The exact 4-coverage area is computed by using Equations 9.