In 2006, the Cost of a Particular Piece of Computer $\$ 490$

In 2006, the cost of a particular piece of computer equipment was $\$ 490$ and going down at a rate of $14 \%$ per year. Assuming this percentage remains constant, what is the formula for $C$ , the cost of this equipment in dollars, as a function of $t$ , the number of years since 2006 ?

A) $C=490(0.86) ^{t}$
B) $C=490(-1.14) ^{t}$
C) $C=490(0.14) ^{t}$
D) $C=490(-0.86) ^{t}$