Design a pulley lift for a tray over 2 storeys

My parents have a 2 storey house with the kitchen upstairs and the pool 3 storeys below and wish to be able to transport food, drinks, towels etc down to the pool. As their Christmas present I would like for an engineer to DESIGN a pulley lift for this space and function, and recommend all materials for my father to purchase materials and build. For the design, I am willing to pay $150. - Height from top of balcony rail to take off point at the pool - 5,200mm - Dimensions of tray to be carried - 500mm x 300mm - Weight of tray to be carried - 7kg - purely mechanical, no electrics - need to be able to use the lift either from the top balcony or from the pool area or both - materials to suit an outside beach environment, facing west with high afternoon sun exposure and obviously some salt air. e.g. stainless steel, wood, and glass/ceramic or very high UV stable plastic - there is a post the height of the house that guide points could be attached to - weight of post is 100mm x 100mm I can email pictures of the balcony, pool and drop. If you are in Sydney, an electrical lift similar to what we are wanting is in Assembly in Regent Place near George St cinema. They use it for drinks. Mandatories: - 1 x design including measurements for build and instructions for installation - 1 x materials lists with materials, quantity and weights outlined Delivered by: Jan 15 2016 All the best, Lham7389