Jasina has a total of $0.80 in nickels and dimes, and she has 4 more nickels than dimes. Which of the following systems of equations can be used to find out how many ( n ) nickels and ( d ) dimes she has?
a) ( 5n + 10d = 80, n = d + 4 )
b) ( 5n + 10d = 80, n = d - 4 )
c) ( n + d = 80, n = d + 4 )
d) ( n + d = 80, n = d - 4 )