thanks please help

You just bought a set of n flavored syrups to mix into coffee. Since you need the caffeine, but hate the taste of coffee, you mix in exactly four different syrup flavors into each of your drinks. Your coffee will taste good only if the four flavors you mix in are pairwise compatible - that is, if for every pair in the four flavors, those two are compatible. Each pair of flavors is compatible (independently) with probability p. What is the expected number of 4-flavor-combinations that will taste good? (a) Carefully define variables for this problem. [4 points] (b) Calculate the expectation. [7 points]