question about proxy_cache_valid

[s0cke at leech.it]

Hi,

what is the difference between the proxy_cache_valid directive and the 
"inactive" parameter of the proxy_cache_path directive?
When I set "proxy_cache_valid 10m;" and "inactive=1h", how long will the 
request be stored?
And what about the controverse: "proxy_cache_valid 200 1h;" and 
"inactive=10m"?

For some reason my cache still contains a file, that has been deleted on 
my backend 10 hours ago. Both, proxy_cache_valid and inactive= are set 
to 2h. Maybe the two settings have different meanings and I do not 
understand yet.