Beth is working on a design for her garden.  She plans to purchase three young olive trees that will need to be watered early in the morning.  She needs to plant the trees $20$ feet apart so they have room to grow, as shown at right.

She has one rotating sprinkler attached to a timer.  She wants to place the sprinkler so that it will reach all three trees, but not waste a lot of water.  Make a sketch of the situation and describe how Beth should determine where to place the sprinkler.