You first need to calculate the final velocity of the block at the end of 4.5 seconds (first stage of motion):

s = 11 m, u = 0 m/s, t = 4.5 s, v = ?

Acceleration is constant therefore substitute into s = (u + v)t/2 and solve for v.

Second stage of motion:

t = 5.9 s, u = the value of v from above, a = 0 m/s^2, s = ?

Substitute into s = ut + at^2/2 and solve for s.