Two cars A and B initially at rest are moving in same direction with acceleration ${\mathrm{a}}_1$ and ${\mathrm{a}}_2$ respectively. After a certain time, they achieve velocities ${\mathrm{v}}_1$ and ${\mathrm{v}}_2$ respectively and separated are by a distance of 50 m. If $({\mathrm{a}}_1 – {\mathrm{a}}_2) = 4\mathrm{m}/{\mathrm{s}}^2$, then the quantity (${\mathrm{v}}_1$ – ${\mathrm{v}}_2$) will be