Take note that Revenue function (R(x)) is price times demand. 

So, R(x) = (1000 - 2q)q = 1000q - 2q^2. 

That is a quadratic function, which is in the form aq^2 + bq + c 

where a < 0. Hence, the parabola opens downward. So, the maximum value will be found at the vertex.

So, we will solve for q, on vertex (q, r). 

So, q = -b/2a = -1000/2(-2) = 250. 

Hence, for 250 units per week, there will be maximum revenue. 

And for the maximum revenue, we will replace the q by 250 on our revenue function. 

R(250) = 1000(250) - 2(250)^2 = 250000 - 125000 = $125000.