Please check my letter, I'm grateful for correction!!

Dear Sir/Madam

Your order for 4,000 optical laser units

Many thanks for the above-mentioned order. The total sum of the ordered goods will amount to $ 50,300.00.

As already indicated in our offer payment is to be made by opening an irrevocable and confirmed letter of credit.(can I use the abbreviation L/C? Which one is communly used??) which is valid until 30 August 2008.
Delivery will be made, as agreed, CIF London.

Due to a current heavy demand for these laser units the requested delivery period of 4 weeks can not be kept to our agreement. We are therefore suggesting you a delivery period of a further 4 weeks (8 weeks in total).[do I have to write this at all?] Please let us know whether you agree to this new term.

Finally, we want to point out that this order is subject to our general conditions of sale.

We look forward to hearing from you soon.

Yours faithfully