Improve over-long sentence ??

Although our products have been marked up by 5%, as usual, our customers place big orders with us. Therefore, our turnover volume has not fallen. We should try to convince our customers that our product quality is high (so as to increase sales volume).

2011-02-19 17:37:24 補充：
Correction : has not fallen ------> should not fallen

2011-02-19 18:13:06 補充：
Correction : should not fallen -----> should not fall

We will mark it up by only 5% but the customer usually places big orders
with us so the total volume should be not small and try to convince the
customer that our quality is high.

以下時在白板抄回來的 :
although we will mark it up only 5%. So the tatal volume should be not
small since the customer usually places big orders with us. Try to
convince the customer that our quality is hight.

For Grammar check only.
We will mark it up by only 5% as the total volume should be not small since customers usually place big orders with us. Please try to convine customers that our quality is high.

- Do you want to lengthen the sentence besides the grammar check? If this is the case, please do let us know.

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