How to maximize the area under -log(x) curve?
That is no programming question but a mathematics question and if I get the function in your question right, the answer is "wherever the graph hits the x-axis".
But I think that was not what you wanted. Maybe you want the rectangle between O(0,0) and P(x, y)?
Than you still should simply use a cas and a-level mathematics:
A = x*(-15.7log(x)+154.94)
I'm trying to get the x and y coordinates for which the area under the curve: y=-15.7log(x)+154.94 is maximum. I would like to compute this in R or Python. Can someone please help me to find it?

Background: I have data points of sales (y) vs prices (x). I tried fitting a log curve in R: lm(formula = y ~ log(x)) which gave me the above equation. I'm trying to increase the revenue which is the product of sales and prices. Hence the rectangular area under the curve should be maximized.