<image>To understand the development of students' individual specialties in a certain school, a random sample of students was surveyed about their participation in activities such as music, sports, art, calligraphy, etc. (each student can only participate in one activity). The collected data was then compiled and the results are shown in Figure 1.
(1) In this survey, a total of ______ students were sampled;
(2) Calculate the central angle of the sector in the pie chart (Figure 2) that represents the students participating in the "music activity" project;
(3) If the school has 2400 students, estimate the number of students who participate in the "art activity" project. 