A lead bullet travelling at $300\ \text{m/s}$ hits a thick steel plate and comes to a stop inside a dent in it. Half of the bullet's kinetic energy turns into heat that stays in the bullet; the rest goes into the plate and into sound. The specific heat of lead is $125\ \text{J kg}^{-1}\,\text{K}^{-1}$. The rise in the temperature of the bullet, in kelvin, is ____.