Deijah gave Isaiah $6.25 in nickels and quarters. If 12 coins were quarters, how many coins were nickels? Which equation models this problem?

A) 0.25•12+0.05•n=6.25

B) 0.05n+625=0.25•12

C)25+5n=6.25

D) 6.25+0.05=12•0.25