Please answe #$2$ and #$3.$

An automobile having a mass of $1,000kg$ is driven into a brick wall in a safety test. The bumper behaves like a spring with constant $5\mathrm{.}15{10}^6\frac{N}{m}$ and is compressed $2\mathrm{.}75$ cm as the car is brought to rest. What was the speed of the car before impact, assuming no energy is lost in the collision with the wall?