[填空题]
For the system of Fig. 4-32 (Example 4-20) how u)p1)kjh/ pzzff:/* gn)/ty edo ti0j large apuga9(t j ia 6pfh1s41qpo49ut/ 4 sfm mass would box A have to have to prevent any mfts suiapmh(9 q1a ft4j /6494p1pougotion from occurring? Assume $\mu_{\mathrm{s}}=0.30$ .
