A program contains a void function named calc New Price. The function receives two double variables named old Price and new Price. The function multiplies the contents of the old Price variable by 1.1 and then stores the result in the new Price variable. Which of the following is the appropriate function prototype for this function?

a. void calc New Price(double, double);

b. void calc New Price(double &, double);

c. void calc New Price(double, double &);

d. void calc New Price(double &, double &);