Two equally charged particles, held $2\mathrm{.}5{10}^{-3}m$ apart, are released from rest. The initial acceleration of the first particle is observed to be $7\mathrm{.}6\frac{m}{s^2}$ and that of the second to be $13\frac{m}{s^2}.$ If the mass of the first particle is $5\mathrm{.}0{10}^{-7}kg,$ what are $($a$)$ the mass of the second particle and $($b$)$ the magnitude of the charge of each particle?