It doesn't display the cost correctly. It just calculates the total x without taking into account the discount. What would I have to change/add to get the total cost after it calculates the discount?

double cost;

double total_cost;

double value;

int x;

float discount;

cout<<"Enter the number of units sold: ";

cin>> x;

cost=(quantity * 99);

cost=(x * 50);

if (x < 10)

discount=(0.0);

else if (x < 20)

discount=(0.2);

else if ( x < 40 )

discount=(0.3);

else if (x < 50)

discount=(0.4);

else

discount=(0.5);

value=(cost*discount);

total_cost= (cost - value);

cout<<"Total cost " << total_cost;