In a certain code language, 'JIVE’ is coded as ‘1597’ and ‘FIVE’ is coded as ‘5781’. Whatis the code for ‘F’ in the given code language?

Given: 

In a certain code language, 'JIVE’ is coded as ‘1597’ and ‘FIVE’ is coded as ‘5781’.

I, V, E and 1, 5, 7 are common in both.

So, the code of F is 8.