Problem 4: An agricultural researcher is investigating the relationship between fertilizer amount and yield of a corn crop, under two different growing conditions. The levels of fertilizer amount (in pounds) are: 40, 60, 80, and 100. The two growing conditions are "sunny" and "shaded". We want to know whether the effect of fertilizer amount on mean yield is different under the two growing conditions. If so, then which pairs of factor level combinations are NOT significantly different? If not, then which levels of fertilizers are significantly different? [Also, if it is of interest for the researcher to predict the corn yield if 90 pounds of fertilizer were used in shaded conditions, what approach would you take, using these data? Do you make any extra assumption to answer this question?] The data and some SAS code are given on the course website. Write a mini-report describing your data analysis of choice and your conclusions to answer the research questions, and giving your recommendation for the best agricultural practice to get good corn yields.