<image> In order to better understand the mathematics midterm exam performance of senior high school students at a certain school, 40 students were randomly selected from all the senior high school students. Their mathematics scores (with a full score of 100 points, and all scores being integers of no less than 40 points) were divided into six intervals: [40,50), [50,60), …, [90,100]. The frequency distribution histogram is shown in the figure.
(1) Find the value of the real number \(a\) in the figure; 
(2) If there are 1800 senior high school students at the school, estimate the number of students whose mathematics scores are no less than 60 points in this exam.