Answer
The first plan is less than the second plan by an amount of
$3687.31$ $Dollars$
Note, this assumes that you pay the balance off in full at the end of the loan.
Work Step by Step
Plan 1 : Fixed at 18,000 Dollars
$C = 18000$ $Dollars$
Plan 2 : 7.9% interest for the discounted price for 4 years
$C = (18000 - 2000)(1.079)^{4}$
$C = (16000)(1.079)^{4}$
$C\approx21687.31$
Thus, the first plan is less than the second plan by an amount of
$3687.31$ $Dollars$
