Let $A, B$ and $C$ be three points taken on the parabola $y^2=4ax$ with coordinates $\left(a{t}_i^2,2a{t}_i\right)$ $i=1, 2, 3,$ where $t_1, t_2$ and $t_3$ are in $\mathrm{AP}$. If $A{A}^{\mathit{\text{'}}}\mathit{,}\mathit{ }B{B}^{\mathit{\text{'}}}$ and $C{C}^{\text{'}}$, are focal chords and coordinates of $A^{\text{'}},B^{\text{'}},C^{\text{'}}$are $\left(a{t}_i^{\text{'}2},2a{t}_i^{\text{'}}\right), i=1, 2, 3$ then $t_1^{\text{'}}, t_2^{\text{'}}$and $t_3^{\text{'}}$ are in