Hyperbolic Product

$A=t_1, B=t_2, C=t_3, D=t_4$ are four concyclic points on the rectangular hyperbola $xy=900$ .

Find the product $t_1 \cdot t_2 \cdot t_3 \cdot t_4$ .

Note:- We define parametric points on a rectangular hyperbola $xy=c^2$ as $(ct,\frac {c}{t})$ .