SOLUTION STEPS:
  1. Total money = $2,000 + $3,710 = $5,710. This does not change from transfers.
  2. After: B has 4 units, A has 1 unit. 5 units = $5,710, so 1 unit = $1,142.
  3. Transfer from A to B: $2,000 - $1,142 = $858.