Error when build for production

[aswanee]

Error: Type AboutPage in F:/Ionic/bnrashed/Arab-finance-ionic/src/pages/about/about.ts
is part of the declarations of 2 modules:
AppModule in
F:/Ionic/bnrashed/Arab-finance-ionic/src/app/app.module.ts
and AboutPageModule in
F:/Ionic/bnrashed/Arab-finance-ionic/src/pages/about/about.module.ts!
Please consider moving AboutPage in
F:/Ionic/bnrashed/Arab-finance-ionic/src/pages/about/about.ts
to a higher module that imports AppModule in
F:/Ionic/bnrashed/Arab-finance-ionic/src/app/app.module.ts
and AboutPageModule in
F:/Ionic/bnrashed/Arab-finance-ionic/src/pages/about/about.module.ts.
You can also create a new NgModule that exports and includes AboutPage in
F:/Ionic/bnrashed/Arab-finance-ionic/src/pages/about/about.ts
then import that NgModule in AppModule in
F:/Ionic/bnrashed/Arab-finance-ionic/src/app/app.module.ts
and AboutPageModule in
F:/Ionic/bnrashed/Arab-finance-ionic/src/pages/about/about.module.ts.