List the arguments (variables) of which a FX call or put option model price is a function. How does the call and put premium change with respect to a change in the arguments?
Answer: Both put and call options are functions of just six variables: St, E, ri, rus, T ands. While all else remains similar, the price of a European FX call (put) option will raise:
a) The larger (smaller) is S,
b) The smaller (larger) is E,
c) The smaller (larger) is ri,
d) The larger (smaller) is rus,
e) The larger (smaller) rus is relative to ri, and
f) The greater is s.
While rus and ri are not very much different in size, a European FX call and put will increase in price while the option term-to-maturity increases. Though, when rus is extremely much larger than ri, a European FX call will increase in price, although the put premium will decrease, while the option term-to-maturity increases. The opposed is true while ri is very much greater as compared to rus. For American FX options the analysis is less complex. As a longer term American option can be exercised on any date which a shorter term option can be exercised, or a some later date, it follows that the all else remaining similar, the longer term American option will sell at a price as a minimum as large as the shorter term option.