For the estimated equation: y_hat = beta_0_hat + beta_1_hat(X_1) + beta_2_hat(X_2) + beta_3_hat((X_1)^2) + beta_4_hat((X_2)^2) + beta_5_hat(X_1 * X_2). What does beta_5_hat > 0 imply? a.) the predicted effect on y from an increase in x_2 is positive is x_2 is positive b). the predicted effect on y from an increase in x_2 is more positive is x_1 is positive c.) the predicted effect on y from an increase in x_2 is more positive is x_2 is larger d). the predicted effect on y from an increase in x_2 is positive is x_2 is negative. what is the correct