URL rewriting gives a 500 Server error with web.config file and dynamic urls

I've used the code below to try and achieve clean urls for my site search results. However, when I implemented it into my web.config file it threw up a Server 500 Error. What did I do wrong?

There are a few pages that i'm trying to clean, see links below:

mydomain.com/dentists/zipcode/18954/us/

mydomain.com/dentists/name/18954/us/the-persons-name/

mydomain.com/dentists/phone/18954/us/3215558888

mydomain.com/dentists/details/person-company-goes-here/

<?xml version="1.0" encoding="utf-8"?><configuration><system.webServer><rewrite><rules><rule name="Rewrite to store_locator_results.php"><match url="^dentists/zipcode/([0-9]+)/([0-9]+)/([0-9]+)/([_0-9a-z-]+)/([_0-9a-z-]+)/" /><action type="Rewrite" url="store_locator_results.php?lat={R:1}&amp;lng={R:2}&amp;postcode={R:3}&amp;countryIso={R:4}&amp;businessname={R:5}" /></rule></rules><rules><rule name="Rewrite to store_locator_results_by_name.php"><match url="^dentists/name/([0-9]+)/([0-9]+)/([0-9]+)/([_0-9a-z-]+)/([_0-9a-z-]+)/([_0-9a-z-]+)/" /><action type="Rewrite" url="store_locator_results_by_name.php?lat={R:1}&amp;lng={R:2}&amp;postcode={R:3}&amp;countryIso={R:4}&amp;lastname={R:5}&amp;businessname={R:6}" /></rule></rules><rules><rule name="Rewrite to store_locator_results_by_phone.php"><match url="^dentists/phone/([0-9]+)/([0-9]+)/([0-9]+)/([_0-9a-z-]+)/([_0-9a-z-]+)/" /><action type="Rewrite" url="store_locator_results_by_phone.php?lat={R:1}&amp;lng={R:2}&amp;postcode={R:3}&amp;countryIso={R:4}&amp;phone={R:5}" /></rule><rule name="Rewrite to store_locator_results.php"><match url="^dentists/details/([0-9]+)/" /><action type="Rewrite" url="store_info.php?store={R:1}" /></rule></rules><outboundRules><rule name="Rewrite to clean URL" preCondition="IsHTML"><action type="Rewrite" value="/dentists/zipcode/{R:3}/{R:4}" /><action type="Rewrite" value="/dentists/name/{R:3}/{R:4}/{R:5}/" /><action type="Rewrite" value="/dentists/phone/{R:3}/{R:4}/{R:5}/" /><action type="Rewrite" value="/dentists/details/{R:1}/" /></rule><preConditions><preCondition name="IsHTML"><add input="{RESPONSE_CONTENT_TYPE}" pattern="^text/html" /></preCondition></preConditions></outboundRules></rewrite></system.webServer></configuration>