<image>A total of 100 students were randomly selected from a certain primary school, and their height (in centimeters) data was plotted into a frequency distribution histogram (as shown in the image). From the data in the image, it is known that a=________. If we want to select 18 students from the height groups of [120,130), [130,140), and [140,150] using stratified sampling to participate in an activity, the number of students to be selected from the height group of [140,150] should be ________.
