Questions (a) to (d) refer to the following statement. We fitted a model (Model 1) to explain the (log) markup (L_MARKUP) of 554 bank branches as a function of:\ i. the (log) turnover of the branch (L_TURNOVER)\ ii. the (log) number of clients of the branch (L_CLIENTS)\ iii. the salesforce, measured by the number of employees in the branch (SALES_FORCE)\ iv. its SQUARE (SQ_SALES_FORCE)\ v. five dummy variables, denoted by Cj ( j = 1, 2, 3, 4, 5), so the value of Cj is one if the ith branch has the complexity level j, and zero otherwise. Bear in mind that C1 and C5 correspond to the highest and smallest degrees of complexity.\ Model 1