Summarize course revenue

So I have a

Course

Course

Course

Course model and an

Enrollment

Enrollment

Enrollment

Enrollment model.

each

Course

Course

Course

Course has a fee.

the

Course

Course

Course

Course model has a function that calculates the revenue like so:

    public function getRevenueAttribute()
    {
        return $this->enrollments()->where('is_paid', true)->count() * $this->cost;
    }

    public function getRevenueAttribute()
    {
        return $this->enrollments()->where('is_paid', true)->count() * $this->cost;
    }

    public function getRevenueAttribute()
    {
        return $this->enrollments()->where('is_paid', true)->count() * $this->cost;
    }

    public function getRevenueAttribute()
    {
        return $this->enrollments()->where('is_paid', true)->count() * $this->cost;
    }

and I am displaying that data in my table:

TextColumn::make('revenue')
    ->state(fn ($record) => $record->revenue)
    ->numeric(),

TextColumn::make('revenue')
    ->state(fn ($record) => $record->revenue)
    ->numeric(),

TextColumn::make('revenue')
    ->state(fn ($record) => $record->revenue)
    ->numeric(),

TextColumn::make('revenue')
    ->state(fn ($record) => $record->revenue)
    ->numeric(),

I want to display the sum of all course revenues at the bottom of my table but adding this didn't help:

->summarize(Sum::make())

->summarize(Sum::make())

->summarize(Sum::make())

->summarize(Sum::make())

instead I get this error