Liquid ammonia ionizes to slight extent. At -50°C, its self-ionization constant, K = [NH4+][NH2-] = — AITS & Test Series Chemistry Question

Question

Liquid ammonia ionizes to slight extent. At -50°C, its self-ionization constant, K = [NH4+][NH2-] = 10^-30 M^2. How many amide ions are present per ml of pure liquid ammonia? (N_A = 6×10^23)