Which of the following Java statements correctly declares a constant?

a$.$

constant mRATE $=3\mathrm{.}5$;

b$.$

constant MORTGAGE$\_$RATE $=3\mathrm{.}5$;

c$.$

double mORTGAGE$\_$RATE $=3\mathrm{.}5$;

d$.$

final double MRATE $=3\mathrm{.}5$;