Breaking Up Calculations

I have a problem where a number (example: 203 cubic meters) needs to be broken up into different prices, like this:

First 70 cubic meters - $5.00 minimum cost
Next 100 cubic meters - 5.0 cents per cubic meter
Next 230 cubic meters - 2.5 cents per cubic meter
Above 400 cubic meters - 1.5 cents per cubic meter

The total charges for 203 cubic meters would be $10.83. For my calculations, I have:

cost1 = (gasused/70) * 5.00;
cost2 = (gasused/100) * 0.05;
cost3 = (gasused/230) * 0.025;
cost4 = (gasused/400) * 0.015;
totalcharges = cost1 + cost2 + cost3 + cost4;

My answer doesn't come out correctly. If anyone has any hints or suggestions, you would make me very, very happy!!!!

Ashley

This should really be in the algorithms forum IMHO, but I'll bite and help you solve your homework. The main problem I see off hand is your formula. IMHO, it should be:

cost1 = (volume below 70 cubic metres * 5.00 / 70)
cost2 = (volume between 71 and 170 gallons) * 0.05
cost3 = (volume between 171 and 400 gallons) * 0.025
cost4 = (volume greater than 400 gallons) * 0.015

I did code the above logic in C (since this is a C forum after all) to test out my theory and obtained $10.825 for 203 cubic metres.

Sorry I'm in the wrong place, but thank you for your help!

Oops! Change gallons to cubic metres in all the above