Equation of travelling wave on a stretched string of linear density $5 \mathrm {~g} / \mathrm { m }$ is $\mathrm { y } = 0.03 \sin ( 450 \mathrm { t } - 9 \mathrm { x } )$ where distance and time are measured in SI units. The tension in the string is:\\
(1) 10 N\\
(2) 7.5 N\\
(3) 12.5 N\\
(4) 5 N