At $9$ am on $20$th November Mr Chan, $("$Chan$")$ received a faxed pro forma standard form contract from HK Paper Ltd:"Premium XX photocopy paper at HK$$500$ per box of $2,000$ pages per box, $500$ boxes available to you as our special customer, with delivery to your office on $1$st day of each calendar month with payment to be paid on delivery COD."Within $1$ hour of receiving the fax Chan signed the contract and ordered $400$ boxes for delivery on $1$st December.Before faxing the form with the details of his order, Chan wrote a note at the foot of the contract"In view of the very large quantity i$.$e$.400$ boxes that I am purchasing from you today, I expect a reduction from you of HK$$50$ per box from your original price of HK$$500$ per box to HK$$450$as a discount for such a large quantity."On $1$st December no delivery of boxes arrived.

Is there a relevant case law about this case $?$