Question 110194
Let X be the units sold,
:
P is the price per unit,
:
R be the total revenue.
:
If R = XP, and the demand equation for the the product is P = 60-0.0004X. 
:
R = XP
Substitute (60-.0004X) for P (from the above equation)
R = X*(60-.0004X)
:
R = 60X - .0004X^2
or
-.0004X^2 + 60X = R
:
It says,"How many units must be sold to produce revenue of $220,000 ?"
:
Substitute 220000 for R in the above equation:
:
-.0004X^2 + 60X = 220000
:
-.0004X^2 + 60X - 220000 = 0; a quadratic equation
:
Solve this for x using the quadratic formula, positive solution:
x = 146,239 (rounded) units sold to make $220,000