Sampling and estimation — practice question

This biased spinner has four faces. Each face has a different colour: yellow, red, green or black. The probability, $p$, that it lands on red is not known. The spinner was spun 200 times, and the sample proportion, $a$, of spins that landed on red was recorded. That proportion was then used to work out an approximate $90\%$ confidence interval for $p$. The interval width was $0.1066$ correct to 4 significant figures.