The value of a baseball player's rookie card began to increase once the player retired. When he retired in 1997 his card was worth $6.36. The value has increased by $1.93 each year since then. Express the relationship relating the value of the card y in dollars and the number of years x the player has been in retirement with an equation. Is the relationship between x and y proportional? What was the value of the card in 2007
?