5. Our class is studying the effects of mindfulness on mental health. To help with data collection, we will have the support of ten grade 9, eleven grade 10, twelve grade 11 and thirteen grade 12 students. Showing your calculations,how many different groups of 12 volunteers can we make if:

a) the group must have the same number of students from each grade? [2A]

b) the group must have at least two grade 9 students? [2A]

c) the group must have Reehan and Bianca (both grade 11 students) in it? [2A]