Revenue max is when MR = 0?

Why is TR max at this point?

Thanks.

The key to this is understanding what marginal revenue is. MR is the change in TR when output is increased by 1. Saying that in reverse, TR for an output level is the TR for one unit less of output plus the MR. If you start off with a positive MR this means that when you increase output level by 1 you increase TR. Similarly, if you have a negative MR, this means if you produce 1 more TR will fall. So if you produce up to a point where you have taken advantage of all the positive MR and there positive impact on TR but have not yet began to reduce your TR by producing when MR is negative, then you will be at the maximum. This is when MR=0.

When MR=0, you have reached the point where the additional revenue gained from the sale of an extra unit is going to start to fall. Therefore this point will maximise your revenue.