jessie has $5.40 in nickels and dimes. she knows that the total numbers of coins is 68, and the equation to represent this is n + d = 68, where n is the number of nickels and d is the number of dimes. if jessie needs a system of equations to find the number of each type of coin, what is the second equation of the system?

a. $0.05n + $0.10d = 68
b. n + d = $5.40
c. $0.50n + $0.10d = $5.40
d. $0.05n + $0.10d = $5.40