String A has twice the tension but half the linear mass density as string B, and both

Question:

String A has twice the tension but half the linear mass density as string B, and both strings have the same length.
(a) The frequency of the first harmonic on string A is (1) four times, (2) twice, (3) half, (4) ¼ times that of string B. Explain.
(b) If the lengths of the strings are 2.5 m and the wave speed on string A is 500 m/s, what are the frequencies of the first harmonic on both strings?