A plant population model predicts genotype proportions 0.49, 0.42, and 0.09 in 400 plants. Observed genotype counts are listed. The correct setup must use each observed count and its matching expected count from the model. Prediction: expected genotype proportions 0.49, 0.42, 0.09. Data after calculating expected counts: AA: observed 185, expected 196; Aa: observed 178, expected 168; aa: observed 37, expected 36. Which expression correctly sums the chi-square contribution from each category?