(i) Based on the relationship between MR and TR it can be said that when TR curve is a positively sloped straight line, then MR curve is a horizontal line. MR and demand curve are the same, and the price (AR) *** constant for different output levels. This happens under perfect competition. MR is constant therefore, TR increases at increasing rate. That is why TR is positively sloped strainght line.
(ii) When TR curve is a horizontal straight line, then MR is zero. Therefore, MR curve is also a horizontal straight line and coincides with the output-axis. It is because the units sold is same at every level of output and Marginal revenue is the additional revenue generated from the sale of an additional unit of output.
