Part (a) : The cost of ordering 25 announcements.
we need to substitute with x=25 in the middle function which is {1.25x+15}
so, the cost of ordering 25 announcements = 1.25 * 25 + 15 = $46.25
Part (b) : The cost of ordering 24 announcements.
we need to substitute with x=24 in the upper function which is {1.5x+15}
so, the cost of ordering 24 announcements = 1.5 * 24 + 15 = $51
Part (c): what number of announcements less than 25 is it financially better to purchase 25 announcements?
We need to find x which will give c(x) is greater than $46.25 and less than or equal $51
By graphing the function and making the the boarders of c(x) at $46.25 and $51
The intersection with the function {1.25x+15} will give us the value of x which is 21 and 24
So, The number of announcements less than 25 is financially better to purchase 25 announcements: 21 ≤ x < 25