At 6% per annum, you pay 2% every 4 months. So at the end of the first 4 months you have:
($1750)·(1.02) = $1785
Now suppose you pay off $x after 4 months, where x is half the total amount due at 8 months. You now have $(1785 - x) left. That amount earns 2% interest for the next 4 months:
(1785-x)·(1.02)
We want that amount to equal x, the amount we paid at 4 months:
(1785-x)·(1.02) = x
1820.7 - 1.02x = x
Solve for x. Round to 2 decimal places.