In the Last Presidential Election,before the Candidates Started Their Major

In the last presidential election,before the candidates started their major campaigns,the percentages of registered voters who favored the various candidates were as follows.

After the major campaigns began,a random sample of 400 voters showed that 172 favored the Republican candidate;164 were in favor of the Democratic candidate;and 64 favored the Independent candidate.We are interested in determining whether the proportion of voters who favored the various candidates had changed.
a.Compute the test statistic.
b.Using the p-value approach,test to see if the proportions have changed.
c.Using the critical value approach,test the hypotheses.