The cost of the second scheme is (yuan). (4 points)

(2) If the cost of Option 1 is, then. (5 points)

The cost of the second scheme is (yuan), and it is (yuan) when a=50.

The price difference of each book is (yuan).

When a=60, (yuan),

(yuan),

The price difference of each book is (yuan)

When a=70, (yuan)

(yuan),

The price difference of each book is (yuan).

To sum up, after comparing the price difference of each book in two different schemes, we can know that the first scheme is more economical by mail order.

Please see question 26.

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