A rocket sled accelerates along a long, horizontal rail. Starting from rest, two rockets burn for $10$s$,$ providing a constant acceleration. One rocket then burns out, halving the acceleration, but the other burns for an additional $5$s to boost the sled's speed to $625$ M$/$s$.$ How far has the sled traveled when the second rocket burns out?

A rocket sled accelerates along a long, horizontal rail. Starting from rest, two rockets burn for $10s,$ providing a constant acceleration. One rocket then burns out, halving the acceleration, but the other burns for an additional $5s$ to boost the sled's speed to $625\frac{m}{s}.$ How far has the sled traveled when the second rocket burns out?