Derivation of y = bt^2 for velocity and acceleration

[Genecks]

Homework Statement

The altitude of the space shuttle during the first 30 s of its ascent is described by the expression у = bt², where the constant b has the value 2.9 m/s². Using calculus, obtain an expression for the velocity and acceleration of the space shuttle during this period.

The Attempt at a Solution

y' = 2bt
y'' = 2b

Book is giving me the following for answers:
y' = bt
y'' = b

Am I doing something wrong?

 

[PhanthomJay]

No, your answers are OK, as long as you are sure which is velocity and which is acceleration. I have no idea what the book was thinking by giving those answers.