Equation of a transverse progressive wave in a string is $\mathrm{y}=5\sin \left(400\mathrm{\pi t}-20\mathrm{\pi x}\right)\mathrm{mm}$ where x is in meter and t in second. If the mass of the string is 0.1 kg/m, then the tension in the string is 

• A

  40 N

• B

  20 N

• C

  60 N

• D

  10 N