Flutter Firebase Error (Execution failed for task ':app:mergeExtDexDebug')

I'm new to programming, and I'm very new to flutter and firebase. I'm experimenting with this code (https://github.com/tattwei46/flutter_login_demo), but I've run into an error. Everything should be the same except I changed the google-service.json and GoogleService.plist to match up with my firebase apps, and I edited home-page.dart. Here is what was printed out:

AGPBI: {"kind":"error","text":"Type com.google.android.gms.common.internal.zzf is referenced as an interface from com.google.android.gms.internal.zzcfb.","sources":[{}],"tool":"D8"}

FAILURE: Build failed with an exception.

• What went wrong: Execution failed for task ':app:mergeExtDexDebug'.

  Could not resolve all files for configuration ':app:debugRuntimeClasspath'. Failed to transform artifact 'firebase-analytics-impl.aar (com.google.firebase:firebase-analytics-impl:11.4.2)' to match attributes {artifactType=android-dex, dexing-enable-desugaring=true, dexing-is-debuggable=true, dexing-min-sdk=16}. Execution failed for DexingWithClasspathTransform: /Users/student/.gradle/caches/transforms-2/files-2.1/cfad2a10e4239993e5e793d023977752/jetified-firebase-analytics-impl-11.4.2/jars/classes.jar. Error while dexing.

• Try: Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

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BUILD FAILED in 57s Finished with error: Gradle task assembleDebug failed with exit code 1

Any solutions and/or ideas for what to look for? Flutter doctor reports no issues.