Final answer:
The formula for the least squares line is y = 1.85174x + 0.0835745. Plot this line on the scatter diagram and calculate the correlation coefficient of the variable sales to verify its significance.
Step-by-step explanation:
To find the formula for the least squares line, we can use the equation in the form ŷ = a + bx, where ŷ is the predicted value, a is the y-intercept, b is the slope, and x is the independent variable. From the given options, the correct formula for the least squares line is a) y = 1.85174x + 0.0835745.
To plot the least squares line on the scatter diagram, we can use the equation to determine the y-values for different x-values and then connect the points to draw the line.
To verify the significance of the variable sales, we can calculate the correlation coefficient. If the correlation coefficient is close to 1 or -1, it indicates a strong relationship between the variables and the variable sales is significant in predicting the dependent variable.