Let f(x) be a polynomial of degree 6 and x in which the coefficient of x^6 is 60. If f(x) has roots -1 and 1, then:
a) lim (x→[infinity]) f(x) = [infinity]
b) lim (x→-[infinity]) f(x) = -[infinity]
c) lim (x→[infinity]) f(x) = -[infinity]
d) lim (x→-[infinity]) f(x) = [infinity]