Let the random cariable X be the number of days that a patient needs to be in the hospital. X has the pmf

f(x) = (5-x) / 10 x=1, 2, 3, 4

The patient receives $200 for day one and two, and $100 for days 3 and 4, what's the expected payment to the hospital?

---

I thought that, expected value is the sum of the probability of a certain outcome times the amount to pay for each outcome. So

E(f) = f(1)*200 + f(2)*200 + f(3)*100 + f(4)*100

= 2/5*200 + 3/10*200 + 1/5*100 + 1/10*100

= 80 + 60 + 20 + 10

= $170

But my book has $360 for the answer =/