An engineer is tasked to design a combinational circuit with three inputs x, y, z and one output F to satisfy the following conditions: The output (F) is HIGH (1) only when majority of the inputs (x, y, z) are HIGH. The output (F) is LOW (0) otherwise. What is the logic equation (in minterm form) that best describes the solution?

a. Σ (3, 5, 6, 7)
b. Σ (4, 5, 6, 7)
c. Σ (2, 3, 6, 7)
d. Σ (1, 2, 3, 7)