A = 2/7.19 + 6/7.27 + 12/13.27 + 5/13.44
=> 1/3 A = 2/21.19 + 6/21.27 + 12/39.27 + 5/39.44
= 2. (1/2 (1/19 -1/21) + 6.1/6 . (1/21 - 1/27) + 12.1/12 . (1/27 -1/39 ) + 5.1/5 (1/39 - 1/44) 
= 1/19 - 1/44 = 25/836  => A = 75/836
B =  5/6.19 + 7/6.31 + 5/9.31 + 8/9.44. 
1/4 B = 5/ 24.19 + 7/24.31 + 5/36.31 + 8/36.44.
 = 1/19 - 1/44 =  25/836 => B = 25/209
=> A/b = 3/4