Select ALL the correct answers.

Helga teaches dance classes. She charges for the classes as shown below.

Option 1: $80 per month for five classes
Option 2: $900 per year for 60 classes
Option 3: $174 for 12 classes

Calculate the constant of proportionality for each class. Then select the true statements below.

Option 3 costs $1 more per class than option 1 costs per class.
Option 2 and option 3 cost the same amount per class.
Option 1 costs $1 more per class than option 2 costs per class.
Option 3 costs the least amount per class.
Option 1 and option 3 cost the same amount per class.

- The constant of proportionality for option 1 is $16 per class ($80 ÷ 5).

- The constant of proportionality for option 2 is $15 per class ($900 ÷ 60).
- The constant of proportionality for option 3 is $14.50 per class ($174 ÷ 12).

The true statements are:
- Option 3 costs $1 more per class than option 1 costs per class.
- Option 3 costs the least amount per class.