Three forces, \(( 15 \mathbf { i } + \mathbf { j } ) \mathrm { N } , ( 5 q \mathbf { i } - p \mathbf { j } ) \mathrm { N }\) and \(( - 3 p \mathbf { i } - q \mathbf { j } ) \mathrm { N }\), where \(p\) and \(q\) are constants, act on a particle. Given that the particle is in equilibrium, find the value of \(p\) and the value of \(q\).
(6)