Question
The book shop has a special offer for files:

1 file for $3.10
4 files for $12

Fred wants to buy 10 files. What is the least amount he has to pay?
3 m

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The book shop has a special offer for files:

1 file for $3.10
4 files for $12

Fred wants to buy 10 files. What is the least amount he has to pay?