Special Relativity: Time Dialation

Speeds typical of our everyday lives results in the laws of Classical Mechanics; however, when a particle approaches a reasonably high fraction of light speed ($c$), the time ($t_\text{obs}$) we observe is dilated such that: $t_{obs} = \frac{t}{\sqrt{1 - \frac{v^2}{c^2}}}$ In an obscure Prussian lab, a positron's velocity ($v$) was accelerated to $0.6c$. If $t$, as experienced by the positron, is $200$ $\text{femtoseconds}$, what would we observe as the dilated time?

Hint: Find $t_\text{obs}$ in $\text{fs}$.

David's Special Relativity Set