In an open economy, the supply curve for dollars in the foreing-currency exhange market is vertical, because the supply does not depend on the exchange currency rate.
The supply of dollars in an open economy depends on the interest rate, which is determined by the difference between imports and exports (which is the same as the difference between purchases and sales of foreign capital).
Sliding is a term connected with a Sliding Scale which is a process of adjusting the amount that you pay according to different conditions. That's exactly what Sari is doing.
In the bank reconciliation they will need to add the difference to the company’s cash balance. They subtracted too much (541-514 = $27 difference) from their cash balance. They need to add $27 to their cash balance so that it will be correct and balance with the bank.
