A truck covers 80 m in 17 s while smoothly slowing down to a final speed of 5.6 m/s

a ) find its original speed

b) Final its acceleration

I want check my answer :

a )

Dx = 80 m

t = 17 s

v = 5.6 m/s

v0= ??

by appling the rule

Dx = 1/2(v+v0)t

80 = 1/2(5.6 + v0) 17

v0 = .5 X 80 - 5.6 /17

=2.023 m/s

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b)

v = v0 + at

5.6 = 2.023 + 17a

a = 5.6 -2.023/17 = 0.214

plese help me and wha thw unit of a will be ?