ct'=\frac{ct_0}{\sqrt{1-\frac{v^{2}}{c^{2}}}}=\frac{ct}{\pi}\sqrt{1-\frac{v^{2}}{c^{2}}}=77ct_1=ct_2/77=c\sqrt{t_1\cdot t_2}=c\sqrt{\frac{t\cdot t_0}{\pi}}=\frac{l_0}{\sqrt{1-\frac{v^{2}}{c^{2}}}}