nxCH2=CH-CH=CH2 + nyCH2=CH-CN ---> [(-CH2-CH=CH-CH2-)x(-CH2-CH-CN-)y]n
MC4H6=54g/mol
MC3H3N=53g/mol
54x+53y..............................14y
100......................................8.7
8.7(54x+53y)=1400y =>469.8x+461.1y=1400y=>469.8x=938.9 =>x/y=938.9/469.8=2/1