在android的app/build.gradle文件中添加这些依赖项时出错

dependencies {
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.4.0'
}

plugins {
    id 'com.android.application'
    id 'kotlin-android'
}

android {
    compileSdkVersion 30
    defaultConfig {
        applicationId "com.example.myapp"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

repositories {
    mavenCentral()
    jcenter()
}

dependencies {
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.4.0'
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}