Comma missing on line 5 in script.js

There was a comma missing between 'carred.png' and "yella-car.png".
Comma has been added.
Confusion with speech marks on line 19 in script.js

A back slash used as an escape character for the apostrophe in (It's) so
the script doesn't think it is the end of the quotation. All other
speech marks in this line have been change to single speech marks to
avoid confusion with double speech marks in the middle of a quotation to
avoid the same problem.
Speech Marks all changed

All speech marks have been changed from double speech marks to single
speech marks through all of script.js to keep the code consistant.
Escape characters have been added where need to avoid confusion with
apostrophes.
randomBackgroundColour not defined on line 12 in index.html

Have removed the whole startTimer function as requested in the comment,
this will resolve the problem of randomBackgroundColour not being
defined as it no longer exists. This also resolves a possible future
problem as there is a startTimer function in script.js which wouldn't
have been called onload (as in line 17 of index.html), the startTimer
function in index.html would've been called instead. Now the script.js
startTimer function will load instead.
Not all car images loading

Some of the car picture names were wrong when listed in the array on
line 5 in script.js. Have changed all of the car picture file names to
make them more consistant eg all car-blue.png, car-green.png etc. And
have then changed the names in the array to match. All images now
loading.
Misspelled car-yellow image name

when I changed the car-yellow.png name to keep the files consistant I
misspelled yellow. This has been changed to car-yellow.png.
Simplified if function on line 38 of script.js

Have simplified the condition in this if function, now says >= 5 instead
of 2 conditions with || to say greater than OR equal to.
purchase rate changed on line 49 of script.java

the purchase rate at 1000 meant that the offer given was 100 times too
big, they would be paying more than the value of the car was originally
which makes no sense. Have changed this to 10 as requested, this way it
produces an offer where they can make profit. Spelling mistake changed
on lines 49 and 51 from pruchaseRate to purchaseRate.
None numerical values being used

'3 years' and '4 years' have been used instead of just 3 and 4. This
wouldn't work when being used to calculate something. Have changed
values to 3 and 4 on lines 61 and 62 in index.html.
Some text not appearing when loan being caculated

class should be id on line 97 in index.html, now the total repayable
appears when a loan is calculated.
Interest amount to big

The interest amount should be 50%, with the value of 50 being used the
interest rate is 5000%, have divided by 100 on line 63 of script.js to
make this 50% and make the monthly repayable and total repayable amounts
correct.