When Mrs Brown looks out of her back room window, a bungalow 7m high and 30m beyond her garden fence is just obscured by a shrub in her hedge which is 1.6m high. She wants to choose a tree to plant beside the shrub which, when fully grown, will have the same effect on a small block of flats 20m high beside the bungalow. However, she does not want it to be much bigger than necessary or it will block out her light. The characteristics of some trees are shown below: