Cars a and b travel in a straight line. the distance of a from the starting point is given as a function of time by xa(t) = αt + βt2, with α = 2.60 m/s and β = 1.20 m/s2. the distance of b from the starting point is xb(t) = γt2 - δt3, with γ = 2.80 m/s2 and δ = 0.20 m/s3. (a) which car is ahead just after the two cars leave the starting point? (b) at what time(s) are the cars at the same point? (c) at what time(s) is the distance from a to b neither increasing nor decreasing? (d) at what time(s) do a and b have the same acceleration?