Need to Divide Hours evenly between multiple Fields to Maintain Averages

[00Able]

I am running a test on a production line.

Usually we run one line for each type of Custom Build. So we would have to run 3 separate lines to run Sedans, Cycle, and Coupes. Now after a year worth of data, I know this:
Sedans = 3.2 Custom Builds per Hour
Cycle = 10 Custom Builds per Hour
Coupes = 3.5 Custom Builds per Hour
I also know that my assistance needed is going to be approximately 18% of total hours worked.
I also know that if I add Sedans & Coupes I should average near 3.3 and if I include to the Sedans and Coupes Assistance Hours it will be around 2.6.

I know it sounds confusing so I have added an attachment with all the averages in Yellow, this is a known, but of course it will change based upon production each day but after studying a year’s worth of data this should be close. I have all the equations built into the green shaded areas, so you can see how I get those numbers.

Ok so I set up a test line with all parts for each style, Sedans, Cycle, and Coupes. Since work is getting slow, I am finding it unproductive to keep moving employees to different lines, as there is a lot of downtime for cleanup, before we can make the move.

After we meet our quota, which varies each day, I have an "Varying” amount of time to complete as much of each type of Style as possible. So to be more efficient I have combined a line. I want to evenly distribute the day, so that it keeps our production level the same, as it would be on the regular lines. This way, we don't throw are averages off, because we are changing the format that we do things. Now I realize the day to day are not going to be perfect, but I want to try to figure out, how much time I need to allot for the production of each product.

So in my example you can see I had 4.75 hours today to run this test line.
and to get my averages the closest, I needed to allot 1.25 hours to Sedans, 1.9 hours for Cycles, 0.8 hours for Coupes, and, 0.8 Hours for Assistance.

Does anyone have an idea, how I can try to get this to sort by itself, so that once I know how much time I have to run this line, I know how much time, I should try to allot for each function? Kind of like working a jigsaw puzzle backwards, I have been doing this manually and it is time consuming to try to get it all to equate, again, it does not have to be perfect, but close.

Because tomorrow I might have 6 hours and I have to widdle with this equation for a bit, to find out what I need?

Any suggestions would be appreciated