What do you pay in rent (like, 623.52)? <input type='text' id='old_rent'><br/>
How many bedrooms are there in your apartment? <select id='num_rooms'><option selected>1<option>2<option>3</select><br/>
<input type='button' value='Calculate Rent!' onclick=calculate_rent()><br/>
<ul>
<li>For April 2011, YOU WILL PAY: <span id="april_rent"></span>
<li>Your new permanent rent with MCI increase will be: <span id='perm_rent'></span>
<li>Number of months to pay Retroactive Amount Due: <span id='num_months'></span>
<li>To begin with, your Installment payment each month will be: <span id='installment'></span>
<li>Your Installment payment from 3/1/2012 each month will be: <span id='next_install'></span>
</ul>
<script language="javascript" type="text/javascript">
function calculate_rent() {
var old_rent = document.getElementById('old_rent').value;
if (old_rent.substring(0,1) == '$') {
   old_rent = old_rent.substring(1);
}
var num_rooms = document.getElementById('num_rooms').value;
var mci = 7.67;
var ri = mci*(2.0+1.0*num_rooms);
var increase = .06*old_rent;
var april_rent = 1.0*old_rent+ 1.0*increase;
var perm_rent = 1.0*old_rent + 1.0*ri;
var installment = Math.max(0,increase-ri);
var first_payment = 11*installment;
var num_months;
var next_install;
if (first_payment >= 10*ri) {
num_months = 10*ri/installment;
next_install = 0;
}
else {
next_install = .06*april_rent+1.0*increase-ri;
num_months = 11.0+1.0*(10*ri-first_payment)/(next_install);
}
document.getElementById('april_rent').textContent = '$' + april_rent.toFixed(2);
document.getElementById('perm_rent').textContent = '$' + perm_rent.toFixed(2);
document.getElementById('num_months').textContent = Math.round(num_months);
document.getElementById('installment').textContent = '$' + installment.toFixed(2);
document.getElementById('next_install').textContent = '$' + next_install.toFixed(2);

}
</script>