I need help understanding how to solve problem 2 part a and b. In part a, doesnt the probability of mass function have the formula P(X=k) = (n choose k)p^k(1-p)^n-k ?

The answer course hero provided is simply a table explaining X1, X2, .... X5. I do not think that is correct since the probability of mass function is entirely different.

For part b, do we use the prices to get the mean (mu)? or do we identify the pastries as separate numbers? for ex, the sweet cone as 1, savory scone as 2, etc.

Does the price matter or do we completely ignore it?

For part c,

do we get the mean (expectation) from the prices or somewhere else?