For part B, if the put has a price of $5, then
c + PV(X) = p + s => c = $3.57
So, would we prefer either the put (since 6.43 > 5.00) or the call (since 5.00 > 3.57)? I'm a bit confused.
[NEAS: Use the following logic.
If the call is truly worth $5, the put is worth $Z. If it is selling for $5, it is either overpriced or underpriced. We should buy under-priced securities and sell over-priced securities.
If the put is truly worth $5, the call is worth $Z. If it is selling for $5, it is either overpriced or underpriced. We should buy under-priced securities and sell over-priced securities.
Substitute the figures. The result: we should buy one of the options and sell the other option.]