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
​?