A company makes a pastry called a chocco. During the manufacturing process, the individual choccos are placed in a baking oven. The time it takes to bake them is normally distributed around a mean of 64 min with a standard deviation of 5 min. Thus, distribution of the population of baking times is normal in shape.

(a) When choccos are baked, what is the probability that the mean baking time of four choccos will be 64 min and 45 s or longer?

(b) What proportion of the individual choccos bake in 57 min or less?