Ella Mental has $600$ ft of fencing to enclose two fields. One is to be a rectangle twice as long as it is wide and the other is to be a square. The square field must contain at least $100$ ft squared. The rectangular one must contain at least $800$ ft squared.

a. If $x$ is the width of the rectangular field, what is the domain of $x$?

b. Plot the graph of the total area contained in the two fields as a function of $x$.

c. What is the greatest area that can be contained in the two fields? Justify your answer

By the way, the answers to a, b, c are...(according to the textbook)

a. domain: $20\le x\le 93.333333\dots$

b. $A(x) = 22500 -450x + 4.25x$ squared

c. greatest area $= 17522.2222$

I keep getting the wrong answer for the greatest area.
Please provide me with explanations to each 


Question: What is the English name for Chitra Rajmah?
Answer: we have reached three varieties of common beans (Phaseolus vulgaris) commonly used in India while researching for website.   

kidney beans -  rajma.

pinto beans - chitri wala rajma, printed rajma.

Navy bean - white rajma, white beans, safed rajma.

You can found more about Indian ingredients in English to Hindi here.