Boiller Calc for Railcraft

local temp = 20
local fuel = 0
local hp = true
local hpname = "HP"
local size = 36
local ticks = 0
local hplp_div = 0
local maxtemp = 1000
local heatstep = 0.05
local fuelvalue = {1000, 1600, 1600, 3200, 6400, 3200, 32000, 96000}
local fuelname = {"Bucket of Lava", "Charcoal", "Forestry Peat", "Coal", "Coal Coke", "Creosote Oil", "Forestry Bio Fuel", "Buildcraft Fuel"}

--user input
print("Which Fuel will you use?")
for i = 1,#fuelname do
    print(i..") "..fuelname[i])
end
local fuelindex = tonumber(io.read())

print("What size of Boiler will you use? (1,8,12,18,27,36)")
size = tostring(io.read())

local answer = ""
while not ((answer == "h") or (answer == "H") or (answer == "l") or (answer == "L")) do
    print("(H)igh or (L)ow Pressure?")
    answer = io.read()
end
if (answer == "h") or (answer == "H") then hp = true else hp = false end

if hp then maxtemp = 1000 else maxtemp = 500 end
if hp then hplp_div = 8 else hplp_div = 16 end
while temp < maxtemp do
    --calculate fuel for tick
    local deltafuel = ((6.4 - size * 0.08) / hplp_div) * size * (1 + 8 * (1 - temp / maxtemp))
    fuel = fuel + deltafuel
    --calculate heat change
    local heatchange = heatstep
    if temp < .25*maxtemp then
        heatchange = heatchange + heatstep
    end
    if temp < .5*maxtemp then
        heatchange = heatchange + heatstep
    end
    if temp < .75*maxtemp then
        heatchange = heatchange + heatstep
    end
    heatchange = heatchange / size
    temp = temp + heatchange
    --advance ticks
    ticks = ticks + 1
    --print("tick "..ticks.." temp: "..temp.." C fuel used: "..fuel)
end

local constantfuel = ((6.4 - size * 0.08) / hplp_div) * size * 20 * 3600 / fuelvalue[fuelindex]

if hp then hpname = size.."HP" else hpname = size.."LP" end
print(hpname.." takes "..tostring(ticks/20).." seconds ("..tostring(ticks).." ticks) and "..tostring(fuel/fuelvalue[fuelindex]).." "..fuelname[fuelindex].." to heat up.")
print("It will require "..tostring(constantfuel).." "..fuelname[fuelindex].." per hour once at max heat.")