The initial amount of money that must be spend to replace the computers is P = $280,000. The period of time expected to replace all the computers is t = 8 years = 96 months. The interest rate is r = 6%.
Then, the monthly payment A is given by the formula:
[tex]\begin{gathered} A=P\frac{r(1+r)^t}{(1+r)^t-1} \\ A=280,000\cdot\frac{0.06\cdot(1+0.06)^{96}}{(1+0.06)^{96}-1} \\ A=\text{ \$16,862.74} \end{gathered}[/tex]