Phonological rules for unexploded sounds

What is the rules for sounds that are unexploded, the lesson below will give you the answer. 

(a) A Fortis plosive will be unexploded when standing before another fortis plosives

Examples:
– act / æk̊t /
– stop / stɔp̊t/
– looked / lʊk̊t/
(b) A fortis plosive will be unexploded when standing at the end of the word
– map / mæp̊/
– hot / hɔt̊ /
– book / bʊk̊ /
– cat / kæt̊ /
– tap / tæp̊ /