Variable overhead variance

Sir I just read through the study text And there was this one specific thing about variable overhead vaeiances It said that variable overhead variances are usually valued at direct labour input But sometimes there could be an instance where it gives units And for these instances we have to value the total variable overhead and we can't find the expenditure and efficiency variances Sir i was wondering how do we find the total variable overhead variance when they give it in units instead of hours Do we use budgeted units in calculating the variance(I'm assuming we use budgeted units because I remember that in direct material variances we used budgeted units when to find the total variance when they didnt give kg quantity)