Simple pendulum and harmonic motion

Homework Statement

A simple pendulum is 5.20 m long. What is the period of simple harmonic motion for this pendulum if it is hanging in an elevator that is accelerating upward at 5.90 m/s2?

Homework Equations

T=2pi*(sqrt(L/g))

The Attempt at a Solution

all I did was plug in the value of the length of the pendulum into the equation like so:
T=2pi*(sqrt(5.2/9.8))=4.58s
but this answer is not right? I'm so confused as to what I am supposed to do and why I am given acceleration if I dont even need it.