how the currency rate are change for purchase and sales transaction

1.                   Close the page.

2.                   Go to General ledger > Currencies > Currency exchange rates.

3.                   Click New.

4.                   In the From currency field, enter or select a value.

5.                   In the list, select row 6.

6.                   In the list, click the link in the selected row.

7.                   In the To currency field, enter or select a value.

8.                   In the list, select row 13.

9.                   In the list, click the link in the selected row.

10.               In the From date field, enter a date.

11.               In the To date field, enter a date.

12.               Click Add.

13.               In the Exchange rate field, enter a number.

14.               Click Save.