group 1 problem

group 1 solution

group 2 problem

group 2 solution

group 3 problem

group 3 solution

group 4 problem

group 4 solution

group 5 problem

group 5 solution

group 6 problem

group 6 solution

group 7 problem

group 7 solution

group 8 problem

group 8 solution

group 9 problem

group 9 solution

group 10 problem

group 10 solution

group 11 problem

group 11 solution

group 12 problem

group 12 solution