A dance will be held at school later this year. The school dance committee recorded data they collected prior to the event as well as the results after the dance was held. They were interested in looking at the relationship between the cost per person, ticket prices, and income earned from the event. This information was given to the principal and included the following tables.

Table A
Proposed Price
Per Ticket ($) Number of Students
Interested in Attending
20 200
25 160
40 100
50 80
Table B
Number of
Tickets Sold Total Income ($)
20 700
25 875
40 1,400
50 1,750
Table A shows that the number of students interested in attending the dance with the proposed price per ticket. The constant of variation is .

Table B shows that the total income with the number of tickets sold. The constant of variation is___ .