b) You know or can easily get the following: displacement (s), final velocity (v), acceleration (a). Since this question is a uniform acceleration problem, there is a formula that links s, v, a and t. Use it to calculate t.

c) You know or can easily get the following: displacement (s), initial velocity (u), acceleration (a). Since this question is a uniform acceleration problem, there is a formula that links s, u, a and v. Use it to calculate v. (You could also use conservation of energy since there's no friction. Or you could just use symmetry since there's no friction .....)