An Impulse problem

A light, inextensible string of length $5m$ is hung from a rigid horizontal support. A particle of mass $1kg$ is tied to the free end of the string and held at a point in the same horizontal plane as the other end of the string at a distance of $3m$ from that end. The particle is released and let fall. The acceleration due to gravity is $10m/s^2$ .The impulse in $kg.m/s^2$ received by the string when it is just taut is