The body of this question is divided into four sections: Exercise, Theoretical context, Answer and Questions. I believe this is the right site to ask given that this is a question about "word choice and usage" (from the help center).
In this textbook I'm working on, I encountered an exercise in which I must choose one of the following sentences:
a) I will do my packing this afternoon, if I can find my suitcase.
b) I am doing my packing this afternoon, if I can find my suitcase.
There is no more context surrounding this sentence, it's a multiple choice question.
In the relevant grammar section is says the following about the two tenses.
Will + infinitive
to predict what is going to happen based on past experience or opinion
You must go to India - you'll enjoy it.
in more formal contexts for arrangements which have been made in some detail
The tour will begin at 9. 30 and all visitors to the site will need to wear good walking shoes.
for decisions which are made on the spur of the moment
I think I'll go to Paris next weekend.
- to talk about activities or events which have already been arranged or are definite. The future continuous can also be used in this context. It is a little more formal.
I'm travelling on the Orient Express to Venice. I'll be travelling on the Orient Express to Venice.
- to avoid going to + go we can use the present continuous form of go instead
He's going climbing in the Alps next summer.
- for surprising or unexpected events
Paula is taking her mother on her honeymoon!
Given that it's not a prediction, not a formal a context, nor does it seem to be a decision made on the spur of the moment, I lean towards the use of the present continuous.
Investigating the present continuous gives me even greater confidence that this is the right choice, since we're talking "about activities or events which have already been arranged".
However, the solution given in the book is a), "will do".
- Isn't the book contradicting itself by choosing a)?
- What is the correct answer?
- What did I miss?