请补全短文，每个题目只填一个空。即整篇短文共9个空，分9个填空题填入。此题只填第（6）空答案。 Fill in the blanks of the following letters with the words given below, and change the form when necessary. oblige, inform, prefer, convince, discount, quantity, purchase, quotation, interest Dear Sirs, We are (1) to buy large quantity of corn and should be (2) if you would give us a (3) per metric ton FOB Los Angels, USA and (4) the earliest date you can ship. We used to (5) corn from other sources, but we now (6) to buy from your corporation because we are given o the understanding that you are able to supply larger (7) with a special (8). Besides, we are (9) that your corn is of better quality. We look forward to hearing from you by return. Yours faithfully,