(1) Because the profit of each type A mask is 0.5, the profit of producing type A masks is 0.5 times. ..

Because one * * * produces 50,000 pieces, the number of type B is (5-x). The profit of a single type B mask is 0.3, so the profit of producing a type B mask is 0.3(5-x).

(2) In the first question, the sum of the two formulas is the total profit, that is, y=0.5+0.3(5-x).

The stem of the question requires a not less than 1.8 million, so 1.8 ≤ A, even if only A is given in 8 days, only 0.6*8=4.8 can be given. So A≤4.8.

(3) Question 1. Use the formula in (2): y = 0.5+0.3(5-x) 1.8≤x≤4.8. So 0.56≤y≤ 1.46.

Question 2. Let the total time required be t, t = x/0.6+(5-x)/0.8 = 5x/12+6.25 and 1.8≤x≤4.8.

So when x= 1.8, the value of t is the smallest, that is, the time is the least. At this time, 1.8 million A's and 32,000 B's (that is, 5- 1.8) were produced.

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