Example model: Example Your Business A. Number of calls received per month 100   B. Number of calls to make one sale (conversion rate) 2   C. Number of sales made to Yellow Pages callers (Line A / Line B) 50   D. Average gross profit produced by Yellow Pages $50   E. Total Gross Profit produced by Yellow Pages (Line C X Line D) $2,500   F. Yellow Pages monthly investment $600   G. Net Gross profit gain from Yellow Pages advertising (Line E - Line F) $1,900

In this example, the advertiser received $1,900 per month in gross profit over and above the $600 investment in Yellow Pages advertising.