Thread: help please

I have tried if statements but there are so many of them.
eg

if ((t1 > 0) && (t2 <= 600)
user_rate = (600 - t1) * rate_1;
else if (t1 >= 6) && (t2 <= 1200)
user_rate = (1200 - t1) * rate_2;
esle if (t1 >= 1200) && (t2 <= 1800);
user_rate = (1800 - t1) * rate_3;
else if (user_rate >= 1800) && (t1 <= 2400)
user_rate = (2400 - t1) * rate_4;
else if (t1 >= 1800) && (t1 <= 2400)
user_rate = (2400 - t1) * rate_4;

My problem is when the times overlap each other.

what if the user starts at 1000 and finishes at 1400? etc

Make an extra inclusion guards

if (t1>0 && t1<6 && t2<=600)


U will probably have four for most of them