3 A car travels along a straight road with constant acceleration \(a \mathrm {~ms} ^ { - 2 }\), where \(a > 0\). The car passes through points \(A , B\) and \(C\) in that order. The speed of the car at \(A\) is \(u \mathrm {~ms} ^ { - 1 }\) in the direction \(A B\). The distance \(B C\) is twice the distance \(A B\). The car takes 8 seconds to travel from \(A\) to \(B\) and 10 seconds to travel from \(B\) to \(C\).

1. Find \(u\) in terms of \(a\).
2. Find the speed of the car at \(C\) in terms of \(a\).