[填空题]
Kindergarten studentmxwg- 8n.p,ip s are creating cone-shawz7sc ug,5hxyctta65*x 6+wiped birthday hats from pieces of colorful paper circles. The first step is to cut out a sector of the paper, as illustrated by sector OABC in the diagram below. The paper circles5g xi cahwux, 7ty*ts+w6 zc65 have centre O and . The length of arc ABC is $4\pi$ cm and angle $\mathrm{A}\hat{\mathrm{O}}\mathrm{C}= \dfrac {2\pi} 7$
1.Find the radius of the paper circles, r. cm
2.Find the area of the sector the students cut out, OABC. $cm^2$
