Answer:
First space: 15
Second space: 20
Third space: 0
Fourth space: 20
Explanation:
If the florist decrease x times the value of the bouquet by 1, the number of bouquets sold is 30 plus 3 times x, so we have that:
P(x) = (20 - x)*(30+3x)
P(x) = 600 +30x - 3x2
The vertical axis of the graph represents the profit P(x) of the florist.
So observing the graph, we can see that the maximum profit is 675, and occurs when the value of x is 5, that is, the price of the bouquet is 20 - 5*1 = $15
Looking again to the graph, we see that when x = 20 her profit is zero (the price of each bouquet will be 20 - 20*1 = 0)
The interval of x for which the florist have a positive profit (P(x) > 0) is between x = -10 and x = 20, but the florist cannot make a negative number of one-dollar decrease, so the lower number in the interval should be 0.