Answer:
a) 
H₀ : µd = 0 
 H₁ : µd < 0 
b) 
The test statistic is 
tₙ₋₁ = α / s√n
c)
at 0.10 level of significance, 
tₙ₋₁ , ₐ
t₃₀₋₁ , ₀.₁₀ = t₂₉, ₀.₁₀ = 1.311
d)
given that T(critical) = 1.62
∴ T(critical) = 1.62 > t₂₉, ₀.₁₀ = 1.311
at 10% level of significance,
REJECT H₀
Since 1.62 > 1.311, we can reject the null hypothesis.