How did I get the EVPI in Q4 of Part 2

This is a question worth studying. The table above shows the EMV for the three possible decisions. How much is the most you should pay for perfect information? We can find this by looking at the biggest --- or in this case smallest payoff because these are costs -- and then multiply that payoff with the probabilities, then adding up. That would be the best possible expected value. Then subtract the highest (or in this case lowest) EMV to find the difference that having perfect information would make.

Here we go: 180*04 + 201.25*0.6 = 193 (rounded). The lowest EMV is 198 (rounded). The difference between them is 198 - 193 = 5. You should not pay more than 5 for perfect information. So in correct notation: EVPI = 5. The expected value of perfect information is 5. Note that in this example we are dealing with costs, so want the lowest. If the problem was concerning profits, we would want the highest.