Estimate how long is the jumper in free fall

Solve the following question:

Question: Extreme-sports enthusiasts have been known to jump off the top of El Capitan, a sheer granite cliff of height 910 m in Yosemite National Park. Assume a jumper runs horizontally off the top of El Capitan with speed 4.0 m/s and enjoys a free fall until she is h = 180 m above the valley floor, at which time she opens her parachute.

Part A: How long is the jumper in free fall?

I need help to find how long the jumper in free fall and ignore air resistance.