Is there a rule about which of the effects is applied first?
If you start with Slow its
30 ft base movement halved (from Slow) = 15 ft. – 10 ft. (from Ray of Frost) = 5 ft. movement left
If your start with Ray of Frost its
30 ft base movement – 10 ft. (from Ray of Frost) = 20 ft, then halved (from Slow) = 10 ft. movement left
Which is correct here and where do I find the rules for that?
Thanks for your time.