$3\mathrm{.}7$ Complete the Which is best? row $())$ of the Cost Comparison table on the Cellular worksheet.

a$.$ Notice that the costs associated with Option $2$ are already calculated in the worksheet.

b$.$ Write a formula to display "Option $1"$ if the total cost of Option $1$ is less than the total cost of Option $2$ for that month.

c$.$ If the total cost of Option $2$ is less than the total cost of Option $1,$ display "Option $2".$

d$.$ Otherwise, display $"$No Difference".