Which one of the following completes the program and produces a non-missing value for the variable TOTQUANTITY in the last
observation of the output data set?
A. totquantity + quantity;
B. totquantity = sum(totquantity + quantity);
C. totquantity 0;
sum totquantity;
D. retain totquantity 0;
totquantity = totquantity + quantity;