6 A particle moves in a straight line. At time \(t \mathrm {~s}\), the acceleration, \(a \mathrm {~m} \mathrm {~s} ^ { - 2 }\), of the particle is given by \(a = 36 - 6 t\). The velocity of the particle is \(27 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) when \(t = 2\).

1. Find the values of \(t\) when the particle is at instantaneous rest.
2. Find the total distance the particle travels during the first 12 seconds.