please help me answer this. please answer on an ipad or piece of paper step by step.

A pendulum hangs from the ceiling of a tall building for some reason. A scientist assumes that since the pendulum has a small oscillation angle, that it exhibits simple harmonic motion. The scientist observes that it takes the pendulum 15 minutes to go through 40 complete oscillations. How long is the pendulum? You can assume that this takes place on Earth. 49 2 Factor of change question - How could you change a pendulum so that its period is doubled? There are two possible answers. For full credit, give both. Show your work