Here,
Now, if the company makes a profit, then
As this equation (i) is greater than 0, so the value of the two roots must have different values in different intervals.
Now, from the equation (i), we have
The value of x is greater than 10 ie: x> 10
Or, the value of x is less than and greater than or equal to 0 i.e.
Because advertising cost can not be negative.
So, if the company makes a profit,
The values of .