c++ - Calculation not returning correct value -

asked write program: "a software company sells package retails $99. quantity discounts given according following table:

quantity    discount   10-19       20%   20-49       30%   50-99       40%   100 or more 50% 

write program asks number of units sold , computes total cost of purchase. input validation: make sure number of units greater 0"

this have far:

#include <iostream> #include <string>           //string class- string of text #include <iomanip>          //required setw= field width of value after using namespace std;  int main() {     double sales, charges, numofunits = 0,            ratea = .20, rateb = .30, ratec = .40, rated = .50;      //set numeric output formatting:     cout << fixed << showpoint << setprecision(2);     cout << "enter quantity order: ";     cin >> sales;      // determine discount:     double price=99.0;     if (sales >= numofunits)     if (sales >= 10 && sales <= 19 )     ratea;     charges = price - ratea *sales;     if (sales >= 20 && sales <= 49)     rateb;     charges = price - rateb *sales;     if (sales >= 50 && sales <= 99)     ratec;     charges = price - ratec *sales;     if (sales > 100 )     rated;     charges = price - rated *sales;      cout << "your total price quantity is: $" <<charges           << " per unit."<< endl;     cout << "that invalid number. run program again\n "          << "and enter number greater than\n"           << numofunits << ".\n"; }  

after compiling, output not give me right answers. maybe math wrong, or flow off? suggestions?

i not want write me, maybe give me pointers

you need use braces {} around multi-line conditions

if (sales >= 10 && sales <= 19 )     ratea;     charges = price - ratea *sales; 

is actually

if (sales >= 10 && sales <= 19 )     ratea; charges = price - ratea *sales; 

i.e. ratea executed conditionally , update charges executed.

also, statements ratea; have no effect should either updated or removed.