A Car Dealership Has Been Working to Increase the Number

A car dealership has been working to increase the number of corporate clients leasing vehicles from them. Their three-month campaign hasn't produced a high correlation between the costs of their marketing versus the number of leases. The manager is uncertain whether it's a bad venture or the result of a poor sales effort. His marketing manager points out that they have a database of information including leads, call backs, number of requests for leasing options and a list of new clients in addition to previous corporate clients all broken down by the sales lead. What kind of analysis would best assist the manager in making a final decision about the marketing efforts?