To @OP before sharing any information, especially mathematical formulas we must verify if the information we are sharing is correct, a simple google search will verify the formula if they are correct. Aside from that, I think @OP needs to modify his formula and adopt the correction done by @Saint-loup and @Faisal2202
This has been repeated here over and over but they (newbies) turn blocked ears and pretend as if no one is talking. Read, learn and understand before you think of teaching others. I know knowledge is not measured by our ranks here and some people behind newbies accounts can not underrate but it's also important to identify the areas you are good at and verify what you intend to post before making it to public. There is no point in rushing to teach others when you also need the knowledge. The annoying thing is to abandon the thread after creating one without following up the discussion. I can see that here, the Op followed up and effect the correction given but sadly he refused to acknowledge those who call his attention. Nevertheless, it's a good topic but just like Faisal2202 said, majority of us don't care about the calculation and formula but we focus on the profit and lose on our investment.
By the way, you also corrected the formula for ROI which no one noticed yet, I also did not, but thanks to you. Op should edit the post accordingly unless he/she has a better explanation. 
