Currency Credit Risk--2008AM Q7

The answer said" Compare the forward rate 15 JPY/ZAR and current spot rate 17.5 JPY/ZAR, the short forward party received money and bear the credit risk? Could sb pls help to list the details of the formula to calculate the value of forward? puzzed is it should be V(forward ) =St- Ft=17.5-15? thanks

use the search function, been discussed before