I will be grateful if you would give me an early reply -What do you feel?

One of my most ardent and frequent readers, Dr. A.M Babu posted a query in the comment box. Which of the following usages is correct?
a) I will be grateful if you would give me an early reply.
b) I will be grateful if you will give me an early reply.
I am afraid, both these usages are incorrect. Let’s discuss it:
Sometimes we talk about things which are not facts, situations which are true in certain circumstances or under certain conditions. Usually these sentences contain if or a similar word. There are likely conditions, unlikely conditions, impossible conditions and general conditions.
1. Likely conditions: Things which are very likely to happen fall into this category. In this, two portions of the sentences are connected by if. While the tense of the first half is simple future the second half needs to be in present simple.
Examples:
a) The doctor will see you if you come at nine
b) We will miss the bus if we don’t hurry
c) They won’t come if the weather is bad.
So, Dr. Babu’s sentence must be “I willl be grateful if you give me an early reply” since this is a likely condition.
2. Unlikely condition: Things might happen, but probably not. Here the first half of the sentence will have would and the send half, past simple.
Examples:
a) She would pass if she worked harder
b) He wouldn’t be happy if he lived on his own
3. Impossible condition: Things might not happen at all. The first half of the sentence is formed with a conditional clause and the second half with past perfect.
Examples:
a) I would have told you if I had known myself.
b) We would have been there on time if we had caught the earlier bus.
4. General conditions: Both the half with present simple tense.
Examples:
a) Sara never apologizes if she is late
b) He gets angry if you argue with him
c) How long does milk keep if you don’t have a refrigerator?
(Courtesy: Blisset and Halgarten. UBSPD, London)

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