The fitted equation from a study on infant head circumference is as follows: head circumference = 1.76 + 0.86gestational age - 2.82toxemia + 0.046(gestational agetoxemia) where gestational age is measured in weeks and toxemia is an indicator variable for the mothers toxemia status during pregnancy (1=had toxemia). For infants whose mothers did not have toxemia during pregnancy, what is the effect of an extra two weeks of gestation? What about for those whose mothers had toxemia?What other information or calculations would you need to decide whether to include this effect in the final model?What effect does the last term represent? How would you interpret this effect?