Thin-walled pressure

maria florCan somebody help me about this question? 😀It's an assignment given to us this Christmas vacation. Here is the question:
The tank is fabricated from 1/4 in. steel plate. Calculate the maximum circumferential stress caused by an internal pressure of 200psi. The tank has a shape of ellipse where a=5in. and b=3in.
Please show your solution.

I am sending you the formula but do confirm it from someone else too.
t=p*[(a+b)/root(ab)]/[*circum stress*efficiency of joint*2]
assume efficiency to be 100% or 95%.
here circumferencial stress is variable.
anyway tell me if you get the correct answer by any other way.😛

I used a different formula. My answer in tangential stress is 4ksi. What is the answer you got???