A study targets three delivery methods on students' final grade. Consider using the qualitative variable, delivery methods, as a predictor of final grade(y). Suppose that three delivery methods were: online class, face-to-face class, and hybrid class. a. How many dummy variables are needed? Please just write down the number, for example, 3. Do not write down: number of variables is 3 - just write down 3. b. Suppose E(y) is a function of delivery methods, how many in E(y)? Please just write down the number, for example, 4. Do not write down: number of is 4 - just write down 4. c. Would you consider interaction terms for independent variables? Please just type yes or no.