1# RPC
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3### Introduction
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5This sample shows the data exchange between the frontend and backend of a device. After the offering and quantity are selected at the frontend, the backend calculates the result and displays it at the frontend.
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7### Usage
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91. Touch the blank box of an offering type. The offering selection list is displayed. Select an offering. The corresponding content is displayed in the blank box.
102. Touch **+** or **-** next to the offering selection box and select the quantity of the offering.
113. Touch **Confirm an order**. The total price is displayed.
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13### Constraints
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15This sample can only be run on standard-system devices.
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