A string of length L, mass per unit length +, and tension T is vibrating at its

Question:

A string of length L, mass per unit length +, and tension T is vibrating at its fundamental frequency. What effect will the following have on the fundamental frequency?
(a) The length of the string is doubled, with all other factors held constant.
(b) The mass per unit length is doubled, with all other factors held constant.
(c) The tension is doubled, with all other factors held constant.