A small ball \(B\) of mass 0.2 kg is hit by a bat. Immediately before being hit, \(B\) has velocity \(( 10 \mathbf { i } - 17 \mathbf { j } ) \mathrm { m } \mathrm { s } ^ { - 1 }\). Immediately after being hit, \(B\) has velocity \(( 5 \mathbf { i } + 8 \mathbf { j } ) \mathrm { ms } ^ { - 1 }\). Find the magnitude of the impulse exerted on \(B\) by the bat.
(4)