Find the explicit function for the nth term of the arithmetic sequence.
f(2)= -11 and f(4)= -5
a) f(n)=-14+3(n-1)
b) f(n)= -11*-6^(n-1)
c) f(n)= -11-6(n-1)
d) f(n)= -14*3^(n-1)