I am understanding the below points:
I am not able to understand why we select z-points as negative from table at the end? Should we always consider z-point with negative value?
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The question is seeking for the probability $$p=P(Z>1.98\cup Z<-1.98)=P(Z>1.98) + P(Z<-1.98)$$
And, the Z-table linked is most probably the CDF of standard normal RV, i.e. $F_Z(z)=P(Z\leq z)$. Since this is symmetric with respect to origin, you have $P(Z>1.98) = P(Z\leq -1.98)$. Since the mentioned z-table gives us the probabilities for any $\leq z$, you use the negative value and multiply by $2$: $$p=2P(Z<-1.98)$$
Or, you could've used $P(Z\leq 1.98)=p_z$ and calculate $p=2(1-p_z)$