A = 6.285 (i.e) A = 44/7
B = 10.571
c = 15.857
D = 7.285 (i.e) D = 51/7

EDIT:
Fully solved in paper

So, what are the weights of those 4 pieces...??
Note: All pieces are rounded-off in weights, like, each parts are in complete KGs and note in Grams...
A = 6.285 ~~ 6
B = 10.571 ~~ 11
c = 15.857 ~~ 16
D = 7.285 ~~ 7

may be i am wrong in rounding off



Note:
Even i checked in calculator, value i correct, so round off may wrong



For checking in calculator:
take 4 x 4 linear equation

(equation 1) => 1A +1B -1C +0D = 1
(equation 2) => 0A +1B -1C +1D = 2
(equation 3) => 1A -1B +0C +1D= 3
(equation 4) => 1A +1B +1C +1D = 40