What are the relative rates of reaction of primary, secondary and tertiary alkyly halides in an SN1 substitution?

Explain the reason for your answer?

Thank you so much?

First I'm not an organic chemist. When I took organic it was all memory work. Now it is all mechanisms. So I think I remember it's 3o > 2o > 1o but I can't tell you why. Here is a site that may help you.

http://www.masterorganicchemistry.com/2012/08/08/comparing-the-sn1-and-sn2-reactions/