N-13 is produced at a cyclotron by bombarding water with high-energy protons to produce ¹³NH₃molecules. If a 100.0 mL sample of water has a pH of 10.57 upon exiting the cyclotron, what is the activity of the sample in Ci? The K_b of NH₃ is 1.8 x 10⁻⁵ and the half-life of N-13 is 9.97 minutes.