(2) As shown:
;
(3) According to Group A, there are 20 people, and the total number is 100.
∴20÷ 100×360 =72 ;
(4) The probability of randomly selecting a student's grade at Grade C (6) is:
(5) Let the growth rate be x,
∴25( 1+x) 2 =36，
∴x 1 =0.2，x ^ 2 =-2.2(s)。
The growth rate of ∴ is 20%.