Paul lends $8,000 to Peter. Peter agrees to pay it back in ten annual installments at 7% with the first payment due in o

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Paul lends $8,000 to Peter. Peter agrees to pay it back in
ten annual installments at 7% with the first payment due in one
year. After making four payments, Peter renegotiates to pay off the
debt with four additional payments. The new payments are calculated
so that Paul will get a 6.5% annual yield over the entire
eight-year period.
Determine how much money Peter saved by renegotiating.
A < $550
B ≥ $550 but < $600
C ≥ $600 but < $650
D ≥ $650 but < $700
E ≥ $700