Error cant resolve AppCompatActivity in Android Studio mounted

//in applicationID put your personal app id otherxise wil not work
apply plugin: ‘com.android.utility’

android {
compileSdkVersion 26
defaultConfig {
applicationId “put your personal applicationID ”
minSdkVersion 15
targetSdkVersion 26
versionCode 1
versionName “1.0”
testInstrumentationRunner “android.help.check.runner.AndroidJUnitRunner”
}
buildTypes {
launch {
minifyEnabled false
proguardFiles getDefaultProguardFile(‘proguard-android.txt’), ‘proguard-rules.professional’
}
}
}

dependencies {
implementation fileTree(dir: ‘libs’, embody: [‘*.jar’])
implementation ‘com.android.help:appcompat-v7:26.1.0’
implementation ‘com.android.help.constraint:constraint-layout:1.0.2’
testImplementation ‘junit:junit:4.12’
androidTestImplementation ‘com.android.help.check:runner:1.0.1’
androidTestImplementation ‘com.android.help.check.espresso:espresso-core:3.0.1’
}

source