[填空题]
A 70-g bullet travelixw (3 9:if7vk.js7a:jvilkoing/da -sdz5vj(c at $250\,m/s$ penetrates a block of ice at 0$^{\circ} C$ and comes to rest within the ice. Assuming that the temperature of the bullet doesn’t change appreciably, how much ice is melted as a result of the collision? g