from Gauss law we have E = 2kx/r where x=linear charge density, r=distance from the wire=1.7 m k =9 x 10^9 SI units.....we have been given E = 3.8 x 10^4 N/C ..... so plugging numbers we get
x = 3.59 x 10^ -6 C/ M (coulomb per meter) =linear charge density