A galvanometer gives full scale deflection with 0.006 A current. By connecting it to a $4990 \Omega$ resistance, it can be converted into a voltmeter of range $0-30 \mathrm{~V}$. If connected to a $\frac{2 \mathrm{n}}{249} \Omega$ resistance, it becomes an ammeter of range $0-1.5 \mathrm{~A}$. The value of $n$ is: