select u.name, count(g.grade + s.sent_date)
from grades g, user_web u, solution s, task t
where t.id = s.task_id
and s.id = g.solution_id
and s.student_id = u.id
and g.grade_date = (select max(a.grade_date) from grades a, user_web b, task c
where b.id = u.id and c.id = t.id)
and g.grade < 60
or s.sent_date is null
group by u.name;