A city power plant wishes to install a feed-water heater in its steam generation system. It is estimated that the increase in efficiency will pay for the heater 1 year after it is installed, and a contractor has promised he can install the heater in 5 months. If the venture is undertaken and it is found that the heater does pay for itself in a year by saving $1,400 per month, what amount was paid to the contractor at the last of each month of construction? Assume that the saving of $1,400 occurs at the last of each month and that the money paid to the contractor could have been invested elsewhere at 12% compounded monthly.