Separate contents, packaging and independent packet sums

The contents of a packet of cereal A have a normal mass distribution with mean 625 g and standard deviation 15 g. Packaging has an independent normal distribution with mean 25 g and standard deviation 3 g. Give answers to 3 significant figures.

(a) Find the probability that one packet of A has total mass exceeding 630 g.

(b) Find the probability that the contents of 4 random packets of A exceed 2450 g.

Cereal B contents have normal mass with mean 465 g and standard deviation 10 g. Find the probability that the contents of 4 random packets of B outweigh the contents of 3 random packets of A.