AdMobFree Requires Peers Not Installed

I installed ionic 4 using ionic start blank as a capacitor project and then AdMobFree using
npm install cordova-plugin-admob-free --save
npm install @ionic-native/admob-free --save

package.json from @ionic-native/admob-free has peer dependencies “@ionic-native/core”: “^4.11.0” and “rxjs”: “^5.5.11” while package.json from @ionic-native/core is version 5.0.0-beta15 and package.json from rxjs is version 6.2.2.

I’m getting the messages
npm WARN @ionic-native/admob-free@4.12.2 requires a peer of @ionic-native/core@^4.11.0 but none is installed. You must install peer dependencies yourself.
npm WARN @ionic-native/admob-free@4.12.2 requires a peer of rxjs@^5.5.11 but none is installed. You must install peer dependencies yourself.

What is required to fix this?

I found a solution:
npm uninstall @ionic-native/admob-free
npm install @ionic-native/admob-free@5.0.0-beta.15 --save