<image>The Wenchuan Earthquake in Sichuan touched the hearts of over three million people in Binzhou, and a large number of middle school students across the city extended their helping hands and actively donated money for earthquake relief. A certain class at Zhenxing Middle School in Binzhou conducted a sample survey of voluntary donations by students at their school and obtained a set of data on student donations. The following chart is a statistical graph based on this data, where the heights of the rectangles from left to right are in the ratio of 3:4:5:8:6. It is also known that the total number of students who donated 25 yuan and 30 yuan is 42.

(1) How many people did they survey in total?
(2) What are the mode and median of this data set?
(3) If the school has a total of 1,560 students, estimate the total donation amount from all students.