interpret the coefficient of income .a.As the average income of women over the age of 60 increases by $1000, sales of StrongBones is predicted to increase by $8.47 million, holding population constant. b.As the average income of women over the age of 60 increases by $1000, sales of StrongBones is predicted to increase by $8.47 million.c.As the average income of women over the age of 60 increases by $1000, sales of StrongBones is predicted to increase by $7.62 million, holding population constant.d.As the average income of women over the age of 60 increases by $1000, sales of StrongBones is predicted to increase by $7.62 million.