00 easy, takes a moment to do 10 small recall, takes a minute 20 average application problem, 15-20 minutes 30 moderate difficulty, can take 2 hours 40 hard, is a term project level 50 maybe impossible, A research problem at the time, write up answer for publication.
This scale is logarithmic
M := Math required
HM := Higher math required
M, and HM do not imply difficulty
∇ := Recommended :~
MUST DO
Note that non-∇≠ ~ Don’t bother.
You should work the questions for the length of time recommended at least before you check the solutions. But if it is reasonable to check the solutions in interest of time or utility, then do check the solutions. You should be able to answer that problem clearly and closely related problems.