$100
1) Setting the table, we can check the status of that account. In order to repay the debt. We'll need to make a deposit of $100
Balance | Deposit, and Withdrawals | New balance
0 50 0+50= 50
50 150 50+150=200
200 -300 200 -300 = -100
-100 100 -100 +100= 0
2) So the amount needed to repay the current debt is $100