title: error in 'com.android.support:appcompat-v7:28.0.0-rc02' and application get crashed
body: <p>After adding an firebase to your applicatio,I got this error message(All com.android.support libraries must use the exact same version specification (mixing versions can lead to runtime crashes). Found versions 28.0.0-rc02, 26.1.0. Examples include com.android.support:animated-vector-drawable:28.0.0-rc02 and com.android.support:support-v4:26.1.0). and when i run my application it get crash. 
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