Allison has a horse stall cleaning business that has been growing rapidly since she started it three years ago. She estimates the total number of horse stalls in her market to be 5000, owned by a total potential population of 1500. Currently, there are only two competitors in the market, Allison, who has 521 stalls that she cleans, and Sam's Hayfaring Maneger, that cleans 1,430 stalls. The remainder of the stalls are cleaned by their owners rather than by a service. Allison prices her cleaning services at $11 per stall per month and Sam charges $8 for the same service. Allison's sales are derived from 121 customers while Sam's are from 63 customers, meaning that Sam's customers have more stalls on a per capita basis. What is the market penetration rate based on potential customers?