The number of telephone calls N between two cities A and B varies directly as the population P\(_{A}\), P\(_B\) respectively and inversely as the square of the distance D between A and B. Which of the following equations represents this relation?
A. N = \(\frac{kp_A}{D^2} + {cp_B}{D^2}\) B. N = \(\frac{k P_{A} P_{B} }{D^2}\) C. N = \(\frac{kD_AP_D}{B^2}\) D. N = \(\frac{kD^2_AP_D}{B}\)
