Multiplying two columns in yii2

I want to multiply two columns in yii2 and get its total in other column grid view i am trying is this but it is not giving the desired output how can I solve this issue.

<?= GridView::widget([

        //'dataProvider' => $dataProvider,

        'dataProvider'=>new ActiveDataProvider([

          'query' => Adanalytics::find()->

                where(['publisher_id' =>  Yii::$app->user->identity->id ])->

                select('id,ad_id,MAX(impression) AS impression, MAX(view) AS view, MAX(clicks) AS clicks,MAX(cpc) AS cpclick,MAX(cpv) AS cpview, (MAX(clicks)*MAX(cpc)) AS totalccost')->

                groupBy('ad_id, visitor_ip'),


        'filterModel' => $searchModel,

        'columns' => [

            ['class' => 'yii\grid\SerialColumn'],

















            ['class' => 'yii\grid\ActionColumn'],


    ]); ?>

I have solved this problem using SQL query and added a total column at the bottom of the same.