Which equation can be used to solve the following word problem?
Emilio has 6 more nickels than dimes, and the total value of his coins is $2.10. How many nickels does he have? Let n represent the number of nickels.
a. 0.10n+0.05n+6=2.10.
b. 0.10(n-6)+0.05n=2.10.
c. 0.10n=0.05(n+6)=2.10.
d. 0.10(n+6)+0.05n=2.10.