\(\mathbb P(X>250)=1-\mathbb P(X\le250)\)
\(\mathbb P(X\le250)=\mathbb P\left(\dfrac{X-200}{20}\le\dfrac{250-200}{20}\right)=\mathbb P(Z\le2.5)\approx0.9938\)
which means
\(\mathbb P(X>250)\approx1-0.9938=0.0062\)
so approximately 0.62% of pandas weight over 250 pounds.
