Hi, I am confused by this relatively simple problem. The operating margin of a business = (Revenue – costs)/Revenue M = (R-C)/R = 1 – C/R Now I wish to find the sensitivity of M to changes in R. So I try to differentiate the equation by R dM/dR = C/R^2 But this equation doesn’t make any sense to me. For example, consider this figures: R=100, C=38, If R increases by 1%, M increases by 0.38%. I am not sure what I am doing wrong. Thanks.