$$Three possibilities have probabilities $0\mathrm{.}5,0\mathrm{.}3$ and $0\mathrm{.}2$ and values $$10,$ $$20,$ and $$30$ respectively. The expected value is:

Question $4$ options:

a$)$

$$$$18$

b$)$

$$$$15$

c$)$

$$$$16$

d$)$

$$$$17$