Communication Systems: JEE Main 2021 Physics question

A signal of 0.1 kW is transmitted in a cable. The attenuation of cable is $-$5 dB per km and cable length is 20 km. The power received at receiver is 10^$-$x W. The value of x is ________. [Gain in $dB = 10{\log _{10}}\left( {{{{P_o}} \over {{P_i}}}} \right)$]