Distinguish six separate rods from three times one rod

Type A rod lengths are normally distributed with mean 5 cm and standard deviation 0.5 cm; type B lengths have mean 10 cm and standard deviation 1 cm. Find the probability that

(a) the total length of 3 type A rods and 2 type B rods lies between 33 and 36 cm,

(b) the total length of 6 type A rods exceeds three times the length of one randomly chosen type B rod.