A college has a total of 2400 students, and each student must select only one subject from the following three options: Data Analysis, Digital Marketing, and Data Management. The details are as follows: 1) The number of girls is 60% of the number of boys. 2) The number of girls who select Digital Marketing as a subject is 25% of the number of boys who choose Data Management as a subject. 3) Half of the girls choose Data Analysis as a subject, and this number is equivalent to 75% of the boys choosing Data Management as a subject. 4) The number of boys opting for Digital Marketing as a subject is 20% less than the number of boys choosing Data Analysis as a subject. Quantity I: Determine the total number of students selecting Digital Marketing as a subject. Quantity II: Determine the total number of students selecting Data Analysis as a subject. Quantity III: Determine the total number of students selecting Data Management as a subject.