Document Analysis on: "To what extent can historians use public art to evaluate national sentiments and tastes?" Please provide substantial information. I am paying for this question.

It is dangerous for historians to use public art, by itself, as a gauge for measuring national sentiments and tastes, largely because the context of the art matters substantially. Some public art is created and installed without prior approval, like the Wall Street Bull was initially. Sometimes these installations are removed and, after popular demand, are returned—again, like the Wall Street Bull. Other times the art installation is removed before significant public engagement is obtained, or the artwork itself is difficult for many people to access.
An additional consideration is who commissions the artwork. During the Renaissance, much of the public artwork was confined to churches or was commissioned by the church or political leaders. The patrons would place demands upon the art, which would impact both the work itself and the sentiments that could be portrayed. This often led to art that was used as propaganda. This same dynamic occurred in the 1930s, when the FDR administration commissioned public artwork that would reflect American pride during the Great Depression. These artworks served as propaganda in order to raise the positives about America in the public consciousness during a time when the citizenry was less than enthusiastic about their own prospects in America.
Finally, some installations, especially those done without permission, can be focused on drawing contrasts between stated values among society and the actions that society takes. In this sense, the artwork is less about demonstrating public sentiment and more about challenging public sentiment.
Art is a complicated subject, and the intentions of the artist can often be different from the takeaways of the viewer. A historian may be able to draw ideas about public sentiment and tastes from broad trends in topics and style, though this will lead to vague conclusions. An examination of the context of various pieces of art (e.g., whether it was installed with or without permission, who commissioned it, and the artist's intent) is necessary to draw more specific conclusions.
For more specific works of art you can examine the various pieces supported by the Federal Art Project (in the United States) and the Cultural Office (in the USSR). You should also look at the different history of the Wall Street Bull and the "Fearless Girl" statue standing in its way. This will give you a better understanding of how public sentiment can be reflected in public artwork in a manner that contrasts with actual public action. Banksy is also an artist whose work should be examined in the present.