The conclusion of a response message should

a. include familiar expressions such as "If I may be of further assistance, please don't hesitate to call me."
b. provide specifics if further action is required.
c. omit the sender's name to avoid legal liability.
d. avoid repeating the information provided or referring to its use.

b. provide specifics if further action is required.

Explanation:

In a response message, one must be cordial and seek to promote GOODWILL with a customer. This can be done by simply referring to any provided information, providing specifics if any further action is required and including the sender's full contact information. Naturally there must also be a tone indicating a willingness to help but not with such cliché phrases such as, " Call me if you need any help". Such responses do not fit well in well written conclusions.