p = initial deposit amount = $1,000
r = periodic interest rate = 5% = 0.05
p2 = adjusted deposit amount

p (1 + r)^-1 + (p + 500) (1 + r)^-2 +

      p2 (1 + r)^-3 + p2 (1 + r)^-4 + p2 (1 + r)^-5 = 4329.48

∴ 2312.925 + 2.47007 p2 = 4329.48

∴ p2 = (4329.48 - 2312.925)/2.47007 = 816.40