The right answer is 150 minutes per week according to the physical activity guidelines.
A moderate activity corresponds to 50% to 70% of this maximum rate, ie 100 to 140 beats per minute for a young person, and 85 to 119 beats per minute for a fiftieth birthday.
Dana is 26 and her bpm is 120. so she's performing moderate physical activity. According to the guidelines, she should exercise 150 minutes of moderate activity and exercise muscle-strengthening activity two days a week.