So the average height of Class A =1700/10 =170 cm.

Total height of Class B =181+179+178+173+170+168+165.

So the average height of Class B =17110 =171.1cm.

② sample variance s of a? =( 12? +9? *2+ 1? +0? +2? *2+7? +8? + 12? )/9

=572/9

③ There are five students in Class B, whose height is not less than 173.

Then the probability of students with 176cm being drawn is 2/5=40%.