If 400 science and technology books are replaced by story books, the number of story books is three times that of science and technology books. If 1000 story books are replaced by science and technology books, the number of story books is 5 / 11 of science and technology books. How many science and technology books are there? How many story books are there?

If 400 science and technology books are replaced by story books, the number of story books is three times that of science and technology books. If 1000 story books are replaced by science and technology books, the number of story books is 5 / 11 of science and technology books. How many science and technology books are there? How many story books are there?

(400 + 1000) / (31 + 3-5111 + 511) = 1400 ／ 716 = 3200 (copies) story books: 3200 ／ (3 + 1) × 3-400 = 2400-400 = 2000 (copies), science and technology books: 3200-2000 = 1200 (copies). Answer: there are 1200 science and technology books and 2000 story books

It is known that the marginal cost function is MC = 3Q ^ 2-30q + 100, and the total cost of producing 10 units of production is 1000
And the average cost function, and the average variable cost function

Suppose that the marginal cost function of a product is C'3q ^ 2-8q + 100. If the total cost of producing 5 units of product is 595, calculate the total cost function and average cost function
How to find the total cost function, average cost function and variable cost function?

Because MC = 3Q ^ 2-8q + 100, the total cost TC = q ^ 3-4q ^ 2 + 100Q + A, where a is constant
Because 595 = 5 ^ 3-4 * 25 + 500 + A, a = 70 is obtained, that is, TC = q ^ 3-4q ^ 2 + 100Q + 70
Average cost AC = TC / Q = q ^ 2-4q + 100 + 70 / Q