Answer:
He should sell 0.988$ per fruit.
Step-by-step explanation:
I. When 15% is rotten so find the remain of good fruits.
    15/100 = x/60
    15 * 60 = 100x
      900/100 = x
       x = 9
Good fruit = total - rotten
         = 60 - 9
So good fruit is 51
II. Find profit of 80% on cost, when cost is 28$
      80/100 = x/28
      2,240 = x100
          x = 22.4
Profit cost = 28 + 22.4
So profit cost is 50.4$
III. Find selling price per fruit, when good fruit is 51 and profit cost is 50.4
     50.4/51 = 0.988
So selling price per fruit is 0.988$
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