Need your help please

[binf]

I have to write a program that is going to read n phone call times (in seconds). And then, the program will calculate the total amount collected from all users.
The first 2 minutes is amount 100.
Every additional 10 seconds amount is 5.
I need the formula to find the total amount every additional 10 seconds (more than 2 minutes)..I wrote this code but it's not ok..Can you help me fix it?

  #include <iostream>
using namespace std;

int callPrice (int sec)
{
    int res=0;
    int i=i+10;
    if (sec<120) res=100;
    else if (sec>120 && sec%10==0) res=100+(sec-120)*5;
    return res;
}

int main ()
{
    int n,time,sum;
    sum=0;
    cin >> n;
    for (int cnt=1;cnt<=n;cnt++)
    {
        cin >> time;
        sum=sum+callPrice(time);
    }
    cout << sum << endl;
    return 0;
}

[keskiverto]

Every call has at least 100.

Take 2 minutes off. If any time remains, divide the remainder by 10. Now you know what to add to the total, don't you?

[JLBorges]

int call_price( int secs )
{
    const int min_cost = 100 ;

    // for call duration up to 120 secs, cost is min_cost
    if( secs <= 120 ) return min_cost ;

    // for call duration > 120 secs, cost is min_cost
    // plus 5 for every additional 10 seconds or part thereof

    int extra_secs = secs - 120 ; // first 120 seconds are already accounted for

    extra_secs += 9 ; // add 9 to round up to next higher multiple of 10
    // 30 => 39/10 == 3
    // 34 => 43/10 == 4
    // 39 => 48/10 == 4

    return  min_cost +  (extra_secs/10) * 5 ;
}

[binf]

thank you very much.. :)