Let:
x = Independent variable = Number of lines
y = Dependent variable = Total cost
b = Cost of the phone plan
a = Cost of each line
a)
The dependent variable is the total cost ( y )
b)
The independent variable is the number of lines ( x )
c)
The function rule is given by:
[tex]\begin{gathered} y=ax+b \\ y=15x+40 \end{gathered}[/tex]d)
x = 4
[tex]\begin{gathered} y(4)=15(4)+40 \\ y(4)=100 \end{gathered}[/tex]The total cost would be $100
