The current cost of a $55$-inch HDTV is $\$1500$ and decreasing by $15\%$ per year.  

1. What is the multiplier?

   Hint (a):

   If the cost decreased by $15\%$ each year, the new cost would be $85\%$ of the previous year.

   Answer (a):

   $0.85$

2. What will a $55$-inch HDTV cost in four years?

   Hint (b):

   In one year the cost will be $\$1500(0.85)$.
   In two years the cost will be $[\$1500(0.85)](0.85)$.
   Continue this pattern.

3. Write an equation to calculate the cost in $n$ years. What does each of the factors in your equation represent?